@article {pmid40826671,
year = {2025},
author = {Manoharan, A and Subramanian, S and Joy, A},
title = {Topological entropy of stationary two-dimensional turbulence.},
journal = {Physical review. E},
volume = {112},
number = {1-2},
pages = {015106},
doi = {10.1103/mdkl-nnq1},
pmid = {40826671},
issn = {2470-0053},
abstract = {Deformation of material lines drives transport and dissipation in many industrial and natural flows. Here, we report an exact Eulerian formula for the stretching rate of a material line, also known as the topological entropy, in a prototype two-dimensional fluid. The only requirement is a distribution of eigenvalues of the strain rate tensor and their decorrelation time. This eliminates the need for Lagrangian tracking in experimental turbulence where particle trajectories are entangled, and thus poorly resolved. Numerical simulations reveal an excellent agreement between our Eulerian estimate and the stretching rate of a Lagrangian material line, over a wide range of Reynolds number.},
}

@article {pmid40783582,
year = {2025},
author = {Zar, PM and Poolaei Moziraji, Z and Azar, AA},
title = {Mathematical modeling of blood flow with copper and graphene nanoparticles in inclined stenotic arteries.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {29155},
pmid = {40783582},
issn = {2045-2322},
mesh = {*Copper/chemistry ; Humans ; *Graphite/chemistry ; *Nanoparticles/chemistry ; *Arteries/physiopathology ; *Models, Cardiovascular ; Models, Theoretical ; Blood Flow Velocity ; Constriction, Pathologic/physiopathology ; Hemodynamics ; },
abstract = {This research investigates hemodynamic behavior in stenosed arteries using a rheological model that integrates hybrid nanoparticles (copper and graphene) suspended in blood. A mathematical framework is developed to analyze flow dynamics in an inclined artery with mild stenosis, incorporating electromagnetic fields, Hall currents, heat generation, and porous media effects governed by Darcy's law. Simplifications under mild stenosis and low Reynolds number conditions enable analytical solutions via the homotopy perturbation method (HPM) and Akbari Ganji Method (AGM). The minimal error observed for axial velocity is [Formula: see text], while that for temperature is [Formula: see text]. Key findings reveal that hybrid nanoparticle enrichment reduces blood flow resistance, and elevated Hall parameters significantly decrease wall shear stress at the arterial boundary. Additionally, an increase in the Darcy number leads to higher axial velocity in all cases. Streamline visualizations demonstrate altered flow patterns in stenosed regions under varying nanoparticle volumes and electromagnetic inputs. Notably, Hall currents exert a pronounced influence on nanoparticle-enhanced flow behavior, underscoring their relevance in biomedical contexts. The efficacy of HPM and AGM in resolving nonlinear momentum equations is validated, supporting their utility in modeling complex bio-nanofluid systems. These insights advance applications in targeted drug delivery, bio-nanofluid mechanics, and therapeutic device design. They offer pathways for optimizing nanoparticle-mediated treatments in cardiovascular diseases and oncology.},
}

*Copper/chemistry
Humans
*Graphite/chemistry
*Nanoparticles/chemistry
*Arteries/physiopathology
*Models, Cardiovascular
Models, Theoretical
Blood Flow Velocity
Constriction, Pathologic/physiopathology
Hemodynamics

@article {pmid40779081,
year = {2025},
author = {Bailey, AA and Guy, RD},
title = {Optimizing metachronal paddling with reinforcement learning at low Reynolds number.},
journal = {The European physical journal. E, Soft matter},
volume = {48},
number = {8-9},
pages = {48},
pmid = {40779081},
issn = {1292-895X},
mesh = {*Swimming/physiology ; *Reinforcement, Psychology ; Biomechanical Phenomena ; *Learning ; *Models, Biological ; Algorithms ; },
abstract = {Metachronal paddling is a swimming strategy in which an organism oscillates sets of adjacent limbs with a constant phase lag, propagating a metachronal wave through its limbs and propelling it forward. This limb coordination strategy is utilized by swimmers across a wide range of Reynolds numbers, which suggests that this metachronal rhythm was selected for its optimality of swimming performance. In this study, we apply reinforcement learning to a swimmer at zero Reynolds number and investigate whether the learning algorithm selects this metachronal rhythm, or if other coordination patterns emerge. We design the swimmer agent with an elongated body and pairs of straight, inflexible paddles placed along the body for various fixed paddle spacings. Based on paddle spacing, the swimmer agent learns qualitatively different coordination patterns. At tight spacings, a back-to-front metachronal wave-like stroke emerges which resembles the commonly observed biological rhythm, but at wide spacings, different limb coordinations are selected. Across all resulting strokes, the fastest stroke is dependent on the number of paddles; however, the most efficient stroke is a back-to-front wave-like stroke regardless of the number of paddles.},
}

*Swimming/physiology
*Reinforcement, Psychology
Biomechanical Phenomena
*Learning
*Models, Biological
Algorithms

@article {pmid40757994,
year = {2025},
author = {Cocconi, L and Shi, Y and Vilfan, A},
title = {Information-Optimal Mixing at Low Reynolds Number.},
journal = {Physical review letters},
volume = {135},
number = {3},
pages = {037101},
doi = {10.1103/cl9m-cmhb},
pmid = {40757994},
issn = {1079-7114},
abstract = {Mutual information between particle positions before and after mixing provides a universal assumption-free measure of mixing efficiency at low Reynolds number that accounts for the kinematic reversibility of the Stokes equation. For a generic planar shear flow with time-dependent shear rate, we derive a compact expression for the mutual information as a nonlinear functional of the shearing protocol and solve the associated extremization problem exactly to determine the optimal control under both linear and nonlinear constraints, specifically total shear and total dissipation per unit volume. Remarkably, optimal protocols turn out to be universal and time-reversal symmetric in both cases. Our results establish a minimum energetic cost of erasing information in a broad class of nonequilibrium drift-diffusive systems.},
}

@article {pmid39865967,
year = {2025},
author = {Weihs, D and Farsani, A and Gurka, R},
title = {Towards a standard application of the Reynolds number in studies of aquatic animal locomotion.},
journal = {The Journal of experimental biology},
volume = {228},
number = {4},
pages = {},
doi = {10.1242/jeb.249896},
pmid = {39865967},
issn = {1477-9145},
mesh = {Animals ; *Swimming/physiology ; Biomechanical Phenomena ; Hydrodynamics ; *Fishes/physiology/anatomy & histology ; *Locomotion ; *Aquatic Organisms/physiology ; },
abstract = {Non-dimensional groups of measured quantities enable comparison between measurements of animals under different conditions and comparison between species. One of the most used such groups is the Reynolds number, which compares inertial and viscous contributions to forces on swimming animals. This group includes two quantities that are chosen by the researcher: a typical length and speed. Choosing these parameters will affect the numerical value of the Reynolds number, defining the state of the fluid flow. For example, by choosing fish body length as opposed to propulsive fin chord, results may vary by an order of magnitude with consequences for analysis and hydrodynamic regimes. Here, we suggest a standardized set of lengths and speeds to be used for aquatic animal locomotion to enable confident utilization of data from different sources. This framework aims to improve comparative studies within the field.},
}

Animals
*Swimming/physiology
Biomechanical Phenomena
Hydrodynamics
*Fishes/physiology/anatomy & histology
*Locomotion
*Aquatic Organisms/physiology

@article {pmid39677972,
year = {2024},
author = {Rosafio, N and Salvadori, S and Misul, DA},
title = {Implementation of a high-order spatial discretization into a finite volume solver: Applications to turbomachinery test cases using an eddy-viscosity turbulence closure.},
journal = {Heliyon},
volume = {10},
number = {16},
pages = {e36478},
pmid = {39677972},
issn = {2405-8440},
abstract = {In this study, the implementation of a high-order spatial discretization method into a Finite Volume solver is presented. Specific emphasis is put on the analysis of the performance over selected turbomachinery test cases. High-order numerical discretization is achieved by adopting the cell-centered Least-Square reconstruction, which is implemented in the in-house solver HybFlow. The validation of the adopted methodology is performed by assessing the solution of a turbulent flat plate with zero pressure gradient, using a eddy-viscosity transitional model. The test case also evidences the effect of the discretization of gradient-based source terms when a high-order reconstruction methodology is used. In the second part of the paper, the solver is used for the solution of relevant two-dimensional turbomachinery test cases, assessing the impact of 2 n d and 3 r d order reconstruction on the prediction of the aerodynamics and the heat transfer for respectively a low-pressure blade and a high-pressure turbine vane. It is shown how a high-order reconstruction allows for obtaining a better prediction of turbomachinery aerodynamics, with lower number of elements. The benefits over heat transfer predictions in high Reynolds number conditions are instead limited to the reduction of heat transfer coefficient spikes in under-resolved regions of the blade. Eventually, the methodology is validated for a three-dimensional low-pressure turbine cascade with realistic boundary layer inflow conditions.},
}

@article {pmid38144068,
year = {2023},
author = {Liu, L and Meng, Z and Zhang, Y and Sun, Y},
title = {Simulation of High-Viscosity Generalized Newtonian Fluid Flows in the Mixing Section of a Screw Extruder Using the Lattice Boltzmann Model.},
journal = {ACS omega},
volume = {8},
number = {50},
pages = {47991-48018},
pmid = {38144068},
issn = {2470-1343},
abstract = {The mixing quality of polymer melts in the mixing section of a single-screw extruder and an injection molding machine has considerable effects on the properties of the molded products. Therefore, the study of the flow field of polymer melts in the mixing section is of great importance. The lattice Boltzmann method (LBM) exhibits unique advantages in simulating non-Newtonian fluids. Many researchers have used LBM to study the flow of medium- and low-viscosity fluids. In their studies, the Reynolds number of fluid flows is generally moderate. However, polymer melts are typical high-viscosity fluids, and their flow Reynolds number is generally very small. The single-relaxation-time lattice Boltzmann method (SRT-LBM) has been used previously to study the flow field of power law fluids in the mixing section. Herein, the flow field of high-viscosity generalized Newtonian fluids in the mixing section of a single-screw extruder is studied using SRT-LBM, the two-relaxation-time lattice Boltzmann method (TRT-LBM), and the multiple-relaxation-time lattice Boltzmann method (MRT-LBM). Through comparison, TRT-LBM has been found to exhibit obvious advantages regarding stability, calculation accuracy, calculation efficiency, and selection of simulation parameters. The TRT-LBM is more suitable for studying high-viscosity generalized Newtonian fluids than SRT-LBM and MRT-LBM. SRT-LBM has low computational efficiency when simulating high-viscosity generalized Newtonian fluids, and instability is easily caused when the fluid has a yield stress. For MRT-LBM, only by studying the relaxation parameters can its advantages be fully utilized. However, optimizing the accuracy and stability of the MRT-LBM via parameter research and linear stability analysis is difficult. For non-Newtonian fluids, it is difficult to optimize the relaxation parameters to make the MRT-LBM more stable and accurate than the TRT-LBM. It is difficult for the MRT-LBM to realize its potential when simulating high-viscosity generalized Newtonian fluids. In addition, we studied the flow pattern in the cross section of the screw channel and compared it to the results reported in previous studies.},
}

@article {pmid36145671,
year = {2022},
author = {Bernad, SI and Socoliuc, V and Susan-Resiga, D and Crăciunescu, I and Turcu, R and Tombácz, E and Vékás, L and Ioncica, MC and Bernad, ES},
title = {Magnetoresponsive Functionalized Nanocomposite Aggregation Kinetics and Chain Formation at the Targeted Site during Magnetic Targeting.},
journal = {Pharmaceutics},
volume = {14},
number = {9},
pages = {},
pmid = {36145671},
issn = {1999-4923},
abstract = {Drug therapy for vascular disease has been promoted to inhibit angiogenesis in atherosclerotic plaques and prevent restenosis following surgical intervention. This paper investigates the arterial depositions and distribution of PEG-functionalized magnetic nanocomposite clusters (PEG_MNCs) following local delivery in a stented artery model in a uniform magnetic field produced by a regionally positioned external permanent magnet; also, the PEG_MNCs aggregation or chain formation in and around the implanted stent. The central concept is to employ one external permanent magnet system, which produces enough magnetic field to magnetize and guide the magnetic nanoclusters in the stented artery region. At room temperature (25 °C), optical microscopy of the suspension model's aggregation process was carried out in the external magnetic field. According to the optical microscopy pictures, the PEG_MNC particles form long linear aggregates due to dipolar magnetic interactions when there is an external magnetic field. During magnetic particle targeting, 20 mL of the model suspensions are injected (at a constant flow rate of 39.6 mL/min for the period of 30 s) by the syringe pump in the mean flow (flow velocity is Um = 0.25 m/s, corresponding to the Reynolds number of Re = 232) into the stented artery model. The PEG_MNC clusters are attracted by the magnetic forces (generated by the permanent external magnet) and captured around the stent struts and the bottom artery wall before and inside the implanted stent. The colloidal interaction among the MNC clusters was investigated by calculating the electrostatic repulsion, van der Waals and magnetic dipole-dipole energies. The current work offers essential details about PEG_MNCs aggregation and chain structure development in the presence of an external magnetic field and the process underlying this structure formation.},
}

@article {pmid36080113,
year = {2022},
author = {Xiao, X and Li, G and Liu, T and Gu, M},
title = {Experimental Study of the Jetting Behavior of High-Viscosity Nanosilver Inks in Inkjet-Based 3D Printing.},
journal = {Nanomaterials (Basel, Switzerland)},
volume = {12},
number = {17},
pages = {},
pmid = {36080113},
issn = {2079-4991},
support = {52005263//National Natural Science Foundation of China/ ; BK20190466//Natural Science Foundation of Jiangsu Province/ ; },
abstract = {Inkjet printing of high-viscosity (up to 10[5] mPa·s) nanosilver inks is an interesting emerging technology to achieve the 3D fully printed fabrication of electronic products. The highly viscous force of the ink makes it impossible to achieve droplet ejection with the traditional piezoelectric-driven drop-on-demand inkjet method. In this study, a pneumatic needle jetting valve is adopted to provide sufficient driving force. A large number of high-viscosity inkjet printing tests are carried out, and the jetting behavior is recorded with a high-speed camera. Different jetting states are determined according to the recorded images, and the causes of their formation are revealed. Additionally, the effects of the operating pressure, preload angle, and fluid pressure on jetting states are elucidated. Furthermore, the jetting phase diagram is obtained with the characterization of the Reynolds number and the printable region is clarified. This provides a better understanding of high-viscosity inkjet printing and will promote the application of high-viscosity inkjet printing in 3D fully printed electronic products.},
}

@article {pmid34845537,
year = {2021},
author = {Patel, K and Stark, H},
title = {Instability of a liquid sheet with viscosity contrast in inertial microfluidics.},
journal = {The European physical journal. E, Soft matter},
volume = {44},
number = {11},
pages = {144},
pmid = {34845537},
issn = {1292-895X},
abstract = {Flows at moderate Reynolds numbers in inertial microfluidics enable high throughput and inertial focusing of particles and cells with relevance in biomedical applications. In the present work, we consider a viscosity-stratified three-layer flow in the inertial regime. We investigate the interfacial instability of a liquid sheet surrounded by a density-matched but more viscous fluid in a channel flow. We use linear stability analysis based on the Orr-Sommerfeld equation and direct numerical simulations with the lattice Boltzmann method (LBM) to perform an extensive parameter study. Our aim is to contribute to a controlled droplet production in inertial microfluidics. In the first part, on the linear stability analysis we show that the growth rate of the fastest growing mode [Formula: see text] increases with the Reynolds number [Formula: see text] and that its wavelength [Formula: see text] is always smaller than the channel width w for sufficiently small interfacial tension [Formula: see text]. For thin sheets we find the scaling relation [Formula: see text], where m is viscosity ratio and [Formula: see text] the sheet thickness. In contrast, for thicker sheets [Formula: see text] decreases with increasing [Formula: see text] or m due to the nearby channel walls. Examining the eigenvalue spectra, we identify Yih modes at the interface. In the second part on the LBM simulations, the thin liquid sheet develops two distinct dynamic states: waves traveling along the interface and breakup into droplets with bullet shape. For smaller flow rates and larger sheet thicknesses, we also observe ligament formation and the sheet eventually evolves irregularly. Our work gives some indication how droplet formation can be controlled with a suitable parameter set [Formula: see text].},
}

@article {pmid33665269,
year = {2021},
author = {Sleiti, AK},
title = {Dataset for measured viscosity of Polyalpha-Olefin- boron nitride nanofluids.},
journal = {Data in brief},
volume = {35},
number = {},
pages = {106881},
pmid = {33665269},
issn = {2352-3409},
abstract = {Datasets of measured viscosity of Polyalpha-Olefin- boron nitride (PAO/hBN) nanofluids are reported. An AR-G2 rheometer (from TA Instruments) experimental setup is used for measuring the rheological property of PAO/hBN nanofluids, which is a combined motor and transducer (CMT) instrument. The test fluid sample size is approximately 1.5 ml and the tests were conducted over a temperature range of the tested fluids from - 20 °C to 70 °C by a water circulator chamber. The dataset includes measured viscosities as a function of the BN volumetric concentration (ϕ) of 0, 0.6 and 1%. Two sets of viscosity measurements are conducted insuring the thermal equilibrium conditions are reached for all experiments. In set (1), the viscosity is measured at intervals of 10 °C by fixing the temperature at each interval (at -20, -10, 0, 10, 20, 30, 40, 50, 60 and 70 °C), while the shear stress and shear rate are varied. In set (2), the temperature is varied from -20 °C to 70 °C at intervals of 0.5 °C, while the shear stress is fixed and the shear rate is varied accordingly. Set (1) is designed to verify whether the fluids are Newtonian or not and set (2) is designed to derive correlations for the viscosity as a function of temperature. Several characteristics data are recorded including rotational speed of the spindle (RPM), torque, viscosity (Pa- s), shear stress (Pa), shear strain rate (1/s) and temperature (°C). The reuse potential of the dataset includes calculating Reynolds number for further flow studies; heat transfer performance studies of nanofluids; lubrication and lubricants' development studies and characteristics of Newtonian and non-Newtonian fluids. The dataset reported here were used (but not published) in the article published by the author in [1] (https://doi.org/10.1016/j.csite.2020.100776).},
}

@article {pmid32901617,
year = {2021},
author = {Oâ Neill, G and Tolley, NS},
title = {Modelling nasal airflow coefficients: an insight into the nature of airflow.},
journal = {Rhinology},
volume = {59},
number = {1},
pages = {66-74},
doi = {10.4193/Rhin19.440},
pmid = {32901617},
issn = {0300-0729},
mesh = {Computer Simulation ; Humans ; Hydrodynamics ; *Nose ; *Pulmonary Ventilation ; },
abstract = {BACKGROUND: There has been considerable discussion and conflicting views regarding the presence of laminar or turbulent flow within the nose. The aim of this study was to investigate how the modelling of variable flow coefficients can assist in the evalua- tion of the characteristics of flow in the resistive segments of the nose.

METHODOLOGY: A comparison was made between the flow coefficient for the nasal valve, obtained from a mathematical model, and resistive flow components such as a Venturi meter and orifice tube. Also, a variable loss coefficient was formulated for the whole (unilateral) nose which, by utilising the intersection of the laminar and turbulent asymptotes, provided an estimation for the critical Reynolds number (Rcrit).

RESULTS: The results show that the flow resistance of the nasal valve is considerably greater than that for both a Venturi meter and an orifice tube implying turbulent or turbulent-like flow for much of nasal inspiration. Regarding the loss coefficient for the whole (unilateral) nose, normal respiration flowrates are displaced well away from the laminar asymptote. The critical Reynolds number was estimated to be 450.

CONCLUSIONS: A novel method of determining the flow characteristics of the nose, particularly the critical Reynolds number, is presented. The analysis indicates a higher degree of turbulence than is assumed from a simple traditional calculation using a hy- draulic diameter and flow through straight tubes. There are implications for computational fluid dynamics (CFD) modelling where either the entire nasal airflow is assumed to be laminar or a low turbulence model implemented.},
}

Computer Simulation
Humans
Hydrodynamics
*Nose
*Pulmonary Ventilation

@article {pmid31718189,
year = {2019},
author = {Zhang, Z and Zhang, P},
title = {Numerical Interpretation to the Roles of Liquid Viscosity in Droplet Spreading at Small Weber Numbers.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {35},
number = {49},
pages = {16164-16171},
doi = {10.1021/acs.langmuir.9b02736},
pmid = {31718189},
issn = {1520-5827},
abstract = {Droplet impacting a free-slip plane at small Weber numbers (We < 30) was numerically investigated by a front tracking method, with particular emphasis on clarifying the roles of the liquid viscosity and the "left-over" internal kinetic energy in droplet spreading. The most interesting discovery is that there exists a certain range of We in which the maximum diameter rate, D̃m, shows a nonmonotonic variation with the Reynolds number, Re. This non-monotonic variation is owing to the dual role of liquid viscosity in influencing droplet spreading. Specifically, when the initial surface energy is comparable to the initial kinetic energy (the corresponding We is around 10-30), the high strain rates of the droplet internal flow dominate its viscous dissipation at a relatively large Re, while the liquid viscosity dominates the viscous dissipation at a relatively small Re. Furthermore, to unravel the influence of droplet attachment and detachment on droplet spreading, we considered two limiting situations such as full attachment (with no gas film throughout droplet spreading) and full detachment (with a gas film throughout droplet spreading). The results show that the droplet with a gas film tends to generate a stronger vortical motion in its rim, results in a larger left-over kinetic energy, and hence causes a smaller spreading.},
}

@article {pmid31611726,
year = {2019},
author = {Holdenried-Chernoff, D and Chen, L and Jackson, A},
title = {A trio of simple optimized axisymmetric kinematic dynamos in a sphere.},
journal = {Proceedings. Mathematical, physical, and engineering sciences},
volume = {475},
number = {2229},
pages = {20190308},
pmid = {31611726},
issn = {1364-5021},
abstract = {Planetary magnetic fields are generated by the motion of conductive fluid in the planet's interior. Complex flows are not required for dynamo action; simple flows have been shown to act as efficient kinematic dynamos, whose physical characteristics are more straightforward to study. Recently, Chen et al. (2018, J. Fluid Mech. 839, 1-32. (doi:10.1017/jfm.2017.924)) found the optimal, unconstrained kinematic dynamo in a sphere, which, despite being of theoretical importance, is of limited practical use. We extend their work by restricting the optimization to three simple two-mode axisymmetric flows based on the kinematic dynamos of Dudley & James (1989, Proc. R. Soc. Lond. A 425, 407-429. (doi:10.1098/rspa.1989.0112)). Using a Lagrangian optimization, we find the smallest critical magnetic Reynolds number for each flow type, measured using an enstrophy-based norm. A Galerkin method is used, in which the spectral coefficients of the fluid flow and magnetic field are updated in order to maximize the final magnetic energy. We consider the t [0] 1 s [0] 1, t [0] 1 s [0] 2 and t [0] 2 s [0] 2 flows and find enstrophy-based critical magnetic Reynolds numbers of 107.7, 142.4 and 125.5 (13.7, 19.6 and 16.4, respectively, with the energy-based definition). These are up to four times smaller than the original flows. These simple and efficient flows may be used as benchmarks in future studies.},
}

@article {pmid31590317,
year = {2019},
author = {Kawaguchi, M and Fukui, T and Funamoto, K and Tanaka, M and Tanaka, M and Murata, S and Miyauchi, S and Hayase, T},
title = {Viscosity Estimation of a Suspension with Rigid Spheres in Circular Microchannels Using Particle Tracking Velocimetry.},
journal = {Micromachines},
volume = {10},
number = {10},
pages = {},
pmid = {31590317},
issn = {2072-666X},
abstract = {Suspension flows are ubiquitous in industry and nature. Therefore, it is important to understand the rheological properties of a suspension. The key to understanding the mechanism of suspension rheology is considering changes in its microstructure. It is difficult to evaluate the influence of change in the microstructure on the rheological properties affected by the macroscopic flow field for non-colloidal particles. In this study, we propose a new method to evaluate the changes in both the microstructure and rheological properties of a suspension using particle tracking velocimetry (PTV) and a power-law fluid model. Dilute suspension (0.38%) flows with fluorescent particles in a microchannel with a circular cross section were measured under low Reynolds number conditions (Re ≈ 10[-4]). Furthermore, the distribution of suspended particles in the radial direction was obtained from the measured images. Based on the power-law index and dependence of relative viscosity on the shear rate, we observed that the non-Newtonian properties of the suspension showed shear-thinning. This method will be useful in revealing the relationship between microstructural changes in a suspension and its rheology.},
}

@article {pmid31236057,
year = {2019},
author = {Cafiero, G and Vassilicos, JC},
title = {Non-equilibrium turbulence scalings and self-similarity in turbulent planar jets.},
journal = {Proceedings. Mathematical, physical, and engineering sciences},
volume = {475},
number = {2225},
pages = {20190038},
pmid = {31236057},
issn = {1364-5021},
abstract = {We study the self-similarity and dissipation scalings of a turbulent planar jet and the theoretically implied mean flow scalings. Unlike turbulent wakes where such studies have already been carried out (Dairay et al. 2015 J. Fluid Mech. 781, 166-198. (doi:10.1017/jfm.2015.493); Obligado et al. 2016 Phys. Rev. Fluids 1, 044409. (doi:10.1103/PhysRevFluids.1.044409)), this is a boundary-free turbulent shear flow where the local Reynolds number increases with distance from inlet. The Townsend-George theory revised by (Dairay et al. 2015 J. Fluid Mech. 781, 166-198. (doi:10.1017/jfm.2015.493)) is applied to turbulent planar jets. Only a few profiles need to be self-similar in this theory. The self-similarity of mean flow, turbulence dissipation, turbulent kinetic energy and Reynolds stress profiles is supported by our experimental results from 18 to at least 54 nozzle sizes, the furthermost location investigated in this work. Furthermore, the non-equilibrium dissipation scaling found in turbulent wakes, decaying grid-generated turbulence, various instances of periodic turbulence and turbulent boundary layers (Dairay et al. 2015 J. Fluid Mech. 781, 166-198. (doi:10.1017/jfm.2015.493); Vassilicos 2015 Annu. Rev. Fluid Mech. 95, 114. (doi:10.1146/annurev-fluid-010814-014637); Goto & Vassilicos 2015 Phys. Lett. A 3790, 1144-1148. (doi:10.1016/j.physleta.2015.02.025); Nedic et al. 2017 Phys. Rev. Fluids 2, 032601. (doi:10.1103/PhysRevFluids.2.032601)) is also observed in the present turbulent planar jet and in the turbulent planar jet of (Antonia et al. 1980 Phys. Fluids 23, 863055. (doi:10.1063/1.863055)). Given these observations, the theory implies new mean flow and jet width scalings which are found to be consistent with our data and the data of (Antonia et al. 1980 Phys. Fluids 23, 863055. (doi:10.1063/1.863055)). In particular, it implies a hitherto unknown entrainment behaviour: the ratio of characteristic cross-stream to centreline streamwise mean flow velocities decays as the -1/3 power of streamwise distance in the region, where the non-equilibrium dissipation scaling holds.},
}

@article {pmid31176976,
year = {2019},
author = {Almohammadi, H and Amirfazli, A},
title = {Droplet impact: Viscosity and wettability effects on splashing.},
journal = {Journal of colloid and interface science},
volume = {553},
number = {},
pages = {22-30},
doi = {10.1016/j.jcis.2019.05.101},
pmid = {31176976},
issn = {1095-7103},
abstract = {HYPOTHESES: The wettability of a surface affects the splashing behavior of a droplet upon impact onto a surface only when surface exhibits either a very high or a very low contact angle. Viscosity affects the splashing threshold in a non-monotony way.

EXPERIMENTS: To examine the roles of drop viscosity and surface wettability on splashing, a wide range of liquid viscosities (1-100 cSt), surface wettabilities (from hydrophilic to hydrophobic), drop velocities (0.5-3.3 m/s), and liquid surface tensions (∼20 and 70 mN/m) were examined. High speed imaging was used.

FINDINGS: Wettability affects the splashing threshold at very extreme limits of the wettability i.e. at very high or very low contact angle values; however, the wettability effect is less prominent on spreading-splashing regime map. For drops of any surface tension impacting surfaces with any wettability, an increase in viscosity (up to ∼5 cSt or Reynolds number of 2000) promotes splashing; whereas using liquids with viscosities larger than 5 cSt, suppress splashing. We explained such behaviors using evolution of the lamella rim, dynamic contact angle, and velocity of the expanding lamella. Finally, to predict the splashing, we developed a general empirical relationship which explains all of ours, and previously reported data.},
}

@article {pmid30830969,
year = {2019},
author = {Khair, AS and Balu, B},
title = {The lift force on a charged sphere that translates and rotates in an electrolyte.},
journal = {Electrophoresis},
volume = {40},
number = {18-19},
pages = {2407-2414},
doi = {10.1002/elps.201900029},
pmid = {30830969},
issn = {1522-2683},
support = {CBET-135064//National Science Foundation/International ; },
mesh = {Colloids/*chemistry ; Diffusion ; Electrolytes/*chemistry ; Electrophoresis/*methods ; Ions/*chemistry ; Kinetics ; Rotation ; },
abstract = {The distortion of the charge cloud around a uniformly charged, dielectric, rigid sphere that translates and rotates in an unbounded binary, symmetric electrolyte at zero Reynolds number is examined. The zeta potential of the particle ζ is assumed small relative to the thermal voltage scale. It is assumed that the equilibrium structure of the cloud is slightly distorted, which requires that the Péclet numbers characterizing distortion due to particle translation, Pet=Ua/D , and rotation, Per=Ωa2/D , are small compared to unity. Here, a is radius of the particle; D is the ionic diffusion coefficient; U=|U| and Ω=|Ω| , where U and Ω are the rectilinear and angular velocities of the particle, respectively. Perturbation expansions for small Pet and Per are employed to calculate the nonequilibrium structure of the cloud, whence the force and torque on the particle are determined. In particular, we predict that the sphere experiences a force orthogonal to its directions of translation and rotation. This "lift" force arises from the nonlinear distortion of the cloud under the combined actions of particle translation and rotation. The lift force is given by Flift=L(κa)(εa3ζ2/D2)U×Ω[1+O(Pet,Per)] . Here, ε is the permittivity of the electrolyte; κ-1 is the Debye length; and L(κa) is a negative function that decreases in magnitude with increasing κa . The lift force implies that an unconstrained particle would follow a curved path; an electrokinetic analog of the inertial Magnus effect. Finally, the implication of the lift force on cross-streamline migration of an electrophoretic particle in shear flow is discussed.},
}

Colloids/*chemistry
Diffusion
Electrolytes/*chemistry
Electrophoresis/*methods
Ions/*chemistry
Kinetics
Rotation

@article {pmid30712603,
year = {2019},
author = {Ibrahim, MG and Hasona, WM and ElShekhipy, AA},
title = {Concentration-dependent viscosity and thermal radiation effects on MHD peristaltic motion of Synovial Nanofluid: Applications to rheumatoid arthritis treatment.},
journal = {Computer methods and programs in biomedicine},
volume = {170},
number = {},
pages = {39-52},
doi = {10.1016/j.cmpb.2019.01.001},
pmid = {30712603},
issn = {1872-7565},
mesh = {Algorithms ; Arthritis, Rheumatoid/*physiopathology/*radiotherapy ; Humans ; Models, Statistical ; *Nanoparticles ; Peristalsis/*radiation effects ; Synovial Fluid/*radiation effects ; Viscosity/*radiation effects ; },
abstract = {BACKGROUND AND OBJECTIVE: The biomedical fluid which fills the Synovial joint cavity is called Synovial fluid which behaves as in the fluid classifications to Non-Newtonian fluids. Also it's described as a several micrometers thick layer among the interstitial cartilages with very low friction coefficient. Consequently, the present paper opts to investigate the influence of the concentration-dependent viscosity on Magnetohydrodynamic peristaltic flow of Synovial Nanofluid in an asymmetric channel in presence of thermal radiation effect.

METHOD: Our problem is solved for two models, in the first model which referred as Model-(I), viscosity is considered exponentially dependent on the concentration. Model-(2), Shear thinning index is considered as a function of concentration. Those models are introduced for the first time in peristaltic or Nanofluid flows literature. The governing problem is reformulated under the assumption of low Reynolds number and long wavelength. The resulting system of equations is solved numerically with the aid of Parametric ND Solve.

RESULTS: Detailed comparisons have been made between Model-(I) and Model-(2) and found unrealistic results between them. Results for velocity, temperature and nanoparticle concentration distributions as well as pressure gradient and pressure rise are offered graphically for different values of various physical parameters.

CONCLUSIONS: Such models are applicable to rheumatoid arthritis (RA) treatment. Rheumatoid arthritis patients can be treated by applying the magnetic field on an electrically conducting fluid, due to the movement of the ions within the cell which accelerates the metabolism of fluids.},
}

Algorithms
Arthritis, Rheumatoid/*physiopathology/*radiotherapy
Humans
Models, Statistical
*Nanoparticles
Peristalsis/*radiation effects
Synovial Fluid/*radiation effects
Viscosity/*radiation effects

@article {pmid30302623,
year = {2019},
author = {Tiwari, A and Chauhan, SS},
title = {Effect of Varying Viscosity on Two-Fluid Model of Blood Flow through Constricted Blood Vessels: A Comparative Study.},
journal = {Cardiovascular engineering and technology},
volume = {10},
number = {1},
pages = {155-172},
doi = {10.1007/s13239-018-00379-x},
pmid = {30302623},
issn = {1869-4098},
mesh = {Arterial Occlusive Diseases/*blood/physiopathology ; Arteries/*physiopathology ; Blood Flow Velocity ; *Blood Viscosity ; *Computer Simulation ; *Erythrocytes ; Humans ; *Models, Cardiovascular ; *Pulsatile Flow ; Regional Blood Flow ; },
abstract = {PURPOSE: Most of the previously studied non-Newtonian blood flow models considered blood viscosity to be constant but for correct measurement of flow rate and flow resistance, the hematocrit dependent viscosity will be better as various literature suggested the variable nature of blood viscosity. Present work concerns the steady and pulsatile nature of blood flow through constricted blood vessels. Two-fluid model for blood is considered with the suspension of all the RBCs (erythrocytes) in the core region as a non-Newtonian (Herschel-Bulkley) fluid and the plasma in the cell free region near wall as a Newtonian fluid. No slip condition on the wall and radially varying viscosity has been taken.

METHODS: For steady flow the analytical approach has been taken to obtain the exact solution. Regular perturbation expansion method has been used to solve the governing equations for pulsatile flow up to first order of approximation by assuming the pulsatile Reynolds number to be very small (much less than unity).

RESULTS: Flow rate, wall shear stress and velocity profile have been graphically analyzed and compared with constant viscosity model. A noteworthy observation of the present study is that rise in viscosity index leads to decay in velocity, velocity of plug flow region, flow rate while flow resistance increases with rising viscosity index (m). The results for Power-law fluid (PL), Bingham-plastic fluid (BP), Newtonian fluid (NF) are found as special cases from this model. Like the constant viscosity model, it has been also observed that the velocity, flow rate and plug core velocity of two-fluid model are higher than the single-fluid model for variable viscosity.

CONCLUSIONS: The two-phase fluid model is more significant than the single-fluid model. Effect of viscosity parameter on various hemodynamical quantities has been obtained. It is also concluded that a rising viscosity parameter (varying nature of viscosity) significantly distinguishes the single and two-fluid models in terms of changes in blood flow resistance. The outcome of present study may leave a significant impact on analyzing blood flow through small blood vessels with constriction, where correct measurement of flow rate and flow resistance for medical treatment is very important.},
}

Arterial Occlusive Diseases/*blood/physiopathology
Arteries/*physiopathology
Blood Flow Velocity
*Blood Viscosity
*Computer Simulation
*Erythrocytes
Humans
*Models, Cardiovascular
*Pulsatile Flow
Regional Blood Flow

@article {pmid30069140,
year = {2018},
author = {Sundstrom, LRJ and Cervantes, MJ},
title = {On the Similarity of Pulsating and Accelerating Turbulent Pipe Flows.},
journal = {Flow, turbulence and combustion},
volume = {100},
number = {2},
pages = {417-436},
pmid = {30069140},
issn = {1573-1987},
abstract = {The near-wall region of an unsteady turbulent pipe flow has been investigated experimentally using hot-film anemometry and two-component particle image velocimetry. The imposed unsteadiness has been pulsating, i.e., when a non-zero mean turbulent flow is perturbed by sinusoidal oscillations, and near-uniformly accelerating in which the mean flow ramped monotonically between two turbulent states. Previous studies of accelerating flows have shown that the time evolution between the two turbulent states occurs in three stages. The first stage is associated with a minimal response of the Reynolds shear stress and the ensemble-averaged mean flow evolves essentially akin to a laminar flow undergoing the same change in flow rate. During the second stage, the turbulence responds rapidly to the new flow conditions set by the acceleration and the laminar-like behavior rapidly disappears. During the final stage, the flow adapts to the conditions set by the final Reynolds number. In here, it is shown that the time-development of the ensemble-averaged wall shear stress and turbulence during the accelerating phase of a pulsating flow bears marked similarity to the first two stages of time-development exhibited by a near-uniformly accelerating flow. The stage-like time-development is observed even for a very low forcing frequency; ω+=ων/u¯τ2=0.00073 (or equivalently, ls+=2/ω+=52), at an amplitude of pulsation of 0.5. Some previous studies have considered the flow to be quasi-steady at ls+=52 ; however, the forcing amplitude has been smaller in those studies. The importance of the forcing amplitude is reinforced by the time-development of the ensemble-averaged turbulence field. For, the near-wall response of the Reynolds stresses showed a dependence on the amplitude of pulsation. Thus, it appears to exist a need to seek alternative similarity parameters, taking the amplitude of pulsation into account, if the response of different flow quantities in a pulsating flow are to be classified correctly.},
}

@article {pmid28187884,
year = {2017},
author = {Shahzadi, I and Sadaf, H and Nadeem, S and Saleem, A},
title = {Bio-mathematical analysis for the peristaltic flow of single wall carbon nanotubes under the impact of variable viscosity and wall properties.},
journal = {Computer methods and programs in biomedicine},
volume = {139},
number = {},
pages = {137-147},
doi = {10.1016/j.cmpb.2016.10.016},
pmid = {28187884},
issn = {1872-7565},
mesh = {*Nanotubes, Carbon ; *Peristalsis ; *Viscosity ; },
abstract = {OBJECTIVE: The main objective of this paper is to study the Bio-mathematical analysis for the peristaltic flow of single wall carbon nanotubes under the impact of variable viscosity and wall properties.

DESIGN/APPROACH: The right and the left walls of the curved channel possess sinusoidal wave that is travelling along the outer boundary. The features of the peristaltic motion are determined by using long wavelength and low Reynolds number approximation. Exact solutions are determined for the axial velocity and for the temperature profile.

FINDINGS: Graphical results have been presented for velocity profile, temperature and stream function for various physical parameters of interest. Symmetry of the curved channel is disturbed for smaller values of the curvature parameter. It is found that the altitude of the velocity profile increases for larger values of variable viscosity parameter for both the cases (pure blood as well as single wall carbon nanotubes). It is detected that velocity profile increases with increasing values of rigidity parameter. It is due to the fact that an increase in rigidity parameter decreases tension in the walls of the blood vessels which speeds up the blood flow for pure blood as well as single wall carbon nanotubes. Increase in Grashof number decreases the fluid velocity. This is due to the reason that viscous forces play a prominent role that's why increase in Grashof number decreases the velocity profile. It is also found that temperature drops for increasing values of nanoparticle volume fraction. Basically, higher thermal conductivity of the nanoparticles plays a key role for quick heat dissipation, and this justifies the use of the single wall carbon nanotubes in different situations as a coolant.

CONCLUSIONS: Exact solutions are calculated for the temperature and the velocity profile. Symmetry of the curved channel is destroyed due to the curvedness for velocity, temperature and contour plots. Addition of single wall carbon nanotubes shows a decrease in fluid temperature. Trapping phenomena show that the size of the trapped bolus is smaller for pure blood case as compared to the single wall carbon nanotubes.},
}

*Nanotubes, Carbon
*Peristalsis
*Viscosity

@article {pmid30213252,
year = {2016},
author = {Tripathi, D and Akbar, NS and Khan, ZH and Bég, OA},
title = {Peristaltic transport of bi-viscosity fluids through a curved tube: A mathematical model for intestinal flow.},
journal = {Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine},
volume = {230},
number = {9},
pages = {817-828},
doi = {10.1177/0954411916658318},
pmid = {30213252},
issn = {2041-3033},
abstract = {The human intestinal tract is a long, curved tube constituting the final section of the digestive system in which nutrients and water are mostly absorbed. Motivated by the dynamics of chyme in the intestine, a mathematical model is developed to simulate the associated transport phenomena via peristaltic transport. Rheology of chyme is modelled using the Nakamura-Sawada bi-viscosity non-Newtonian formulation. The intestinal tract is considered as a curved tube geometric model. Low Reynolds number (creeping hydrodynamics) and long wavelength approximations are taken into consideration. Analytical solutions of the moving boundary value problem are derived for velocity field, pressure gradient and pressure rise. Streamline flow visualization is achieved with Mathematica symbolic software. Peristaltic pumping phenomenon and trapping of the bolus are also examined. The influence of curvature parameter, apparent viscosity coefficient (rheological parameter) and volumetric flow rate on flow characteristics is described. Validation of analytical solutions is achieved with a MAPLE17 numerical quadrature algorithm. The work is relevant to improving understanding of gastric hydrodynamics and provides a benchmark for further computational fluid dynamic simulations.},
}

@article {pmid26158210,
year = {2016},
author = {Ali, N and Javid, K and Sajid, M and Anwar Bég, O},
title = {Numerical simulation of peristaltic flow of a biorheological fluid with shear-dependent viscosity in a curved channel.},
journal = {Computer methods in biomechanics and biomedical engineering},
volume = {19},
number = {6},
pages = {614-627},
doi = {10.1080/10255842.2015.1055257},
pmid = {26158210},
issn = {1476-8259},
mesh = {Body Fluids/physiology ; Humans ; *Models, Theoretical ; Peristalsis/*physiology ; Reproducibility of Results ; Rheology ; Viscosity ; },
abstract = {Peristaltic motion of a non-Newtonian Carreau fluid is analyzed in a curved channel under the long wavelength and low Reynolds number assumptions, as a simulation of digestive transport. The flow regime is shown to be governed by a dimensionless fourth-order, nonlinear, ordinary differential equation subject to no-slip wall boundary conditions. A well-tested finite difference method based on an iterative scheme is employed for the solution of the boundary value problem. The important phenomena of pumping and trapping associated with the peristaltic motion are investigated for various values of rheological parameters of Carreau fluid and curvature of the channel. An increase in Weissenberg number is found to generate a small eddy in the vicinity of the lower wall of the channel, which is enhanced with further increase in Weissenberg number. For shear-thinning bio-fluids (power-law rheological index, n < 1) greater Weissenberg number displaces the maximum velocity toward the upper wall. For shear-thickening bio-fluids, the velocity amplitude is enhanced markedly with increasing Weissenberg number.},
}

Body Fluids/physiology
Humans
*Models, Theoretical
Peristalsis/*physiology
Reproducibility of Results
Rheology
Viscosity

@article {pmid26015833,
year = {2015},
author = {Kim, H and Cheang, UK and Kim, D and Ali, J and Kim, MJ},
title = {Hydrodynamics of a self-actuated bacterial carpet using microscale particle image velocimetry.},
journal = {Biomicrofluidics},
volume = {9},
number = {2},
pages = {024121},
pmid = {26015833},
issn = {1932-1058},
abstract = {Microorganisms can effectively generate propulsive force at the microscale where viscous forces overwhelmingly dominate inertia forces; bacteria achieve this task through flagellar motion. When swarming bacteria, cultured on agar plates, are blotted onto the surface of a microfabricated structure, a monolayer of bacteria forms what is termed a "bacterial carpet," which generates strong flows due to the combined motion of their freely rotating flagella. Furthermore, when the bacterial carpet coated microstructure is released into a low Reynolds number fluidic environment, the propulsive force of the bacterial carpet is able to give the microstructure motility. In our previous investigations, we demonstrated motion control of these bacteria powered microbiorobots (MBRs). Without any external stimuli, MBRs display natural rotational and translational movements on their own; this MBR self-actuation is due to the coordination of flagella. Here, we investigate the flow fields generated by bacterial carpets, and compare this flow to the flow fields observed in the bulk fluid at a series of locations above the bacterial carpet. Using microscale particle image velocimetry, we characterize the flow fields generated from the bacterial carpets of MBRs in an effort to understand their propulsive flow, as well as the resulting pattern of flagella driven self-actuated motion. Comparing the velocities between the bacterial carpets on fixed and untethered MBRs, it was found that flow velocities near the surface of the microstructure were strongest, and at distances far above, the surface flow velocities were much smaller.},
}

@article {pmid25378709,
year = {2014},
author = {Huang, H and He, X},
title = {Interfacial tension based on-chip extraction of microparticles confined in microfluidic Stokes flows.},
journal = {Applied physics letters},
volume = {105},
number = {14},
pages = {143704},
pmid = {25378709},
issn = {0003-6951},
support = {R01 EB012108/EB/NIBIB NIH HHS/United States ; },
abstract = {Microfluidics involving two immiscible fluids (oil and water) has been increasingly used to produce hydrogel microparticles with wide applications. However, it is difficult to extract the microparticles out of the microfluidic Stokes flows of oil that have a Reynolds number (the ratio of inertia to viscous force) much less than one, where the dominant viscous force tends to drive the microparticles to move together with the surrounding oil. Here, we present a passive method for extracting hydrogel microparticles in microfluidic Stokes flow from oil into aqueous extracting solution on-chip by utilizing the intrinsic interfacial tension between oil and the microparticles. We further reveal that the thickness of an "extended confining layer" of oil next to the interface between oil and aqueous extracting solution must be smaller than the radius of microparticles for effective extraction. This method uses a simple planar merging microchannel design that can be readily fabricated and further integrated into a fluidic system to extract microparticles for wide applications.},
}

@article {pmid24032937,
year = {2013},
author = {Prakash, J and Lavrenteva, OM and Nir, A},
title = {Interaction of bubbles in an inviscid and low-viscosity shear flow.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {88},
number = {2},
pages = {023021},
doi = {10.1103/PhysRevE.88.023021},
pmid = {24032937},
issn = {1550-2376},
abstract = {The pressure loads on two identical spherical bubbles impulsively introduced in an inviscid simple shear flow are calculated. The interaction force due to these pressure loads is employed to model the dynamics of air bubbles injected to a low-viscosity fluid sheared in a Couette device at the first shear flow instability where the bubbles are trapped inside the stable Taylor vortex. It was shown that the interaction between the bubbles in the primary shear flow drives them away from each other. The performed simulations revealed that in an inviscid flow the separation distances between equal size bubbles undergo complex periodic motion. The presence of low-viscosity results in a qualitative change of the interaction pattern: The bubbles either eventually assume an ordered string with equal separation distances between all neighbors or some of them collide. The first regime is qualitatively similar to the behavior of bubbles at low Reynolds number [Prakash et al., Phys. Rev. E 87, 043002 (2013)]. Furthermore, if the Reynolds number exceeds some critical value the temporal behavior of the separations becomes nonmonotonic and exhibits over- and undershooting of the equilibrium separations. The latter effects were observed in the experiments, but are not predicted by the low Reynolds number model of the process [Prakash et al., Phys. Rev. E 87, 043002 (2013)].},
}

@article {pmid23368052,
year = {2012},
author = {Kim, Y and Lai, MC},
title = {Numerical study of viscosity and inertial effects on tank-treading and tumbling motions of vesicles under shear flow.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {86},
number = {6 Pt 2},
pages = {066321},
doi = {10.1103/PhysRevE.86.066321},
pmid = {23368052},
issn = {1550-2376},
mesh = {Biophysics/*methods ; Computer Simulation ; Models, Theoretical ; *Motion ; Movement ; Shear Strength ; Stress, Mechanical ; *Viscosity ; },
abstract = {An inextensible vesicle under shear flow experiences a tank-treading motion on its membrane if the viscosity contrast between the interior and exterior fluids is small. Above a critical threshold of viscosity contrast, the vesicle undergoes a tumbling bifurcation. In this paper, we extend our previous work [Kim and Lai, J. Comput. Phys. 229, 4840 (2010)] to the case of different viscosity and investigate the transition between the tank-treading and tumbling motions in detail. The present numerical results are in a good agreement with other numerical and theoretical studies qualitatively. In addition, we study the inertial effect on this transition and find that the inertial effect might inhibit the tumbling motion in favor of the tank-treading motion, which is observed recently in the literature. The critical viscosity contrast for the transition to the tumbling motion usually increases as the reduced area increases in the Stokes regime. However, we surprisingly observe that the critical viscosity contrast decreases as the reduced area increases to some point in the flow of slightly higher Reynolds number. Our numerical result also shows that the inertial effect has stronger inhibition to tumbling motion when the reduced area is small.},
}

Biophysics/*methods
Computer Simulation
Models, Theoretical
*Motion
Movement
Shear Strength
Stress, Mechanical
*Viscosity

@article {pmid23214675,
year = {2012},
author = {Huang, H and Wu, Y and Lu, X},
title = {Shear viscosity of dilute suspensions of ellipsoidal particles with a lattice Boltzmann method.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {86},
number = {4 Pt 2},
pages = {046305},
doi = {10.1103/PhysRevE.86.046305},
pmid = {23214675},
issn = {1550-2376},
abstract = {The intrinsic viscosities for prolate and oblate spheroidal suspensions in a dilute Newtonian fluid are studied using a three-dimensional lattice Boltzmann method. Through directly calculated viscous dissipation, the minimum and maximum intrinsic viscosities and the period of the tumbling state all agree well with the analytical solution for particles with different aspect ratios. This numerical test verifies the analysis on maximum and minimum intrinsic viscosities. Different behavior patterns of transient intrinsic viscosity in a period are analyzed in detail. A phase lag between the transient intrinsic viscosity and the orientation of the particle at finite Reynolds number (Re) is found and attributed to fluid and particle inertia. At lower Re, the phase lag increases with Re. There exists a critical Reynolds number Rea at which the phase lag begins to decrease with Re. The Rea depends on the aspect ratio of the particle. We found that both the intrinsic viscosity and the period change linearly with Re when ReRea (high-Re regime). In the high-Re regime, the dependence of the period on Re is consistent with a scaling law, and the dependence of the intrinsic viscosity on Re is well described by second-degree polynomial fits.},
}

@article {pmid22817394,
year = {2014},
author = {Tripathi, D and Pandey, SK and Siddiqui, A and Bég, OA},
title = {Non-steady peristaltic propulsion with exponential variable viscosity: a study of transport through the digestive system.},
journal = {Computer methods in biomechanics and biomedical engineering},
volume = {17},
number = {6},
pages = {591-603},
doi = {10.1080/10255842.2012.703660},
pmid = {22817394},
issn = {1476-8259},
mesh = {Body Fluids/metabolism ; Humans ; Intestines/physiology ; *Models, Biological ; *Peristalsis ; Pressure ; Stress, Mechanical ; Viscosity ; },
abstract = {A theoretical study is presented for transient peristaltic flow of an incompressible fluid with variable viscosity in a finite length cylindrical tube as a simulation of transport in physiological vessels and biomimetic peristaltic pumps. The current axisymmetric analysis is qualitatively similar to two-dimensional analysis but exhibits quantitative variations. The current analysis is motivated towards further elucidating the physiological migration of gastric suspensions (food bolus) in the human digestive system. It also applies to variable viscosity industrial fluid (waste) peristaltic pumping systems. First, an axisymmetric model is analysed in the limit of large wavelength ([Formula: see text]) and low Reynolds number ([Formula: see text]) for axial velocity, radial velocity, pressure, hydromechanical efficiency and stream function in terms of radial vibration of the wall ([Formula: see text]), amplitude of the wave ([Formula: see text]), averaged flow rate ([Formula: see text]) and variable viscosity ([Formula: see text]). Subsequently, the peristaltic flow of a fluid with an exponential viscosity model is examined, which is based on the analytical solutions for pressure, wall shear stress, hydromechanical efficiency and streamline patterns in the finite length tube. The results are found to correlate well with earlier studies using a constant viscosity formulation. This study reveals some important features in the flow characteristics including the observation that pressure as well as both number and size of lower trapped bolus increases. Furthermore, the study indicates that hydromechanical efficiency reduces with increasing magnitude of viscosity parameter.},
}

Body Fluids/metabolism
Humans
Intestines/physiology
*Models, Biological
*Peristalsis
Pressure
Stress, Mechanical
Viscosity

@article {pmid22400654,
year = {2012},
author = {Noskov, V and Denisov, S and Stepanov, R and Frick, P},
title = {Turbulent viscosity and turbulent magnetic diffusivity in a decaying spin-down flow of liquid sodium.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {85},
number = {1 Pt 2},
pages = {016303},
doi = {10.1103/PhysRevE.85.016303},
pmid = {22400654},
issn = {1550-2376},
abstract = {The free decay of a strong flow of liquid sodium (at Reynolds number defined via the maximal mean velocity and the radius of the channel cross section up to Re≈3×10(60) and the corresponding magnetic Reynolds number up to Rm≈30) generated by the sudden stop of a rapidly rotating toroidal channel is studied experimentally. The toroidal and poloidal components of velocity are measured using a potential probe. We describe the onset of motion, the evolution of strongly anisotropic fluctuations, and the homogenization and decay of turbulence in the final period. We analyze the statistical characteristics of velocity fields in relation to the behavior of effective magnetic diffusivity estimated from measurements of the phase shift between the induced and applied magnetic fields. For the late (self-similar) decay of turbulent flow, turbulent viscosity is shown to be dependent on the root-mean-square velocity pulsations and can be expressed as νt∼νRe1.3. The behavior of turbulent magnetic diffusivity depends on the magnetic Reynolds number defined in terms of the root-mean-square velocity pulsations. At low magnetic Reynolds numbers (Rmrms<1), turbulent magnetic diffusivity grows rapidly with increasing velocity pulsations (ηt∼ηRmrms2). If the magnetic Reynolds number exceeds unity, the behavior of turbulent magnetic diffusivity becomes similar to the behavior of turbulent viscosity. The highest values of turbulent magnetic diffusivity are achieved at the end of braking, which corresponds to the transient stage of a strongly anisotropic turbulent flow in which the poloidal velocity oscillations prevail.},
}

@article {pmid21635091,
year = {2011},
author = {Nguyen van Yen, R and Farge, M and Schneider, K},
title = {Energy dissipating structures produced by walls in two-dimensional flows at vanishing viscosity.},
journal = {Physical review letters},
volume = {106},
number = {18},
pages = {184502},
doi = {10.1103/PhysRevLett.106.184502},
pmid = {21635091},
issn = {1079-7114},
abstract = {We perform numerical experiments of a dipole crashing into a wall, a generic event in two-dimensional incompressible flows with solid boundaries. The Reynolds number (Re) is varied from 985 to 7880, and no-slip boundary conditions are approximated by Navier boundary conditions with a slip length proportional to Re(-1). Energy dissipation is shown to first set up within a vorticity sheet of thickness proportional to Re(-1) in the neighborhood of the wall, and to continue as this sheet rolls up into a spiral and detaches from the wall. The energy dissipation rate integrated over these regions appears to converge towards Re-independent values, indicating the existence of energy dissipating structures that persist in the vanishing viscosity limit.},
}

@article {pmid21036338,
year = {2010},
author = {Fischer, MW and Stolze-Rybczynski, JL and Davis, DJ and Cui, Y and Money, NP},
title = {Solving the aerodynamics of fungal flight: how air viscosity slows spore motion.},
journal = {Fungal biology},
volume = {114},
number = {11-12},
pages = {943-948},
pmid = {21036338},
issn = {1878-6146},
support = {R15 ES016425/ES/NIEHS NIH HHS/United States ; 1R15 ES016425/ES/NIEHS NIH HHS/United States ; },
mesh = {Fungi/*chemistry/cytology ; Models, Biological ; Spores, Fungal/*chemistry/cytology ; Viscosity ; },
abstract = {Viscous drag causes the rapid deceleration of fungal spores after high-speed launches and limits discharge distance. Stokes' law posits a linear relationship between drag force and velocity. It provides an excellent fit to experimental measurements of the terminal velocity of free-falling spores and other instances of low Reynolds number motion (Re<1). More complex, non-linear drag models have been devised for movements characterized by higher Re, but their effectiveness for modeling the launch of fast-moving fungal spores has not been tested. In this paper, we use data on spore discharge processes obtained from ultra-high-speed video recordings to evaluate the effects of air viscosity predicted by Stokes' law and a commonly used non-linear drag model. We find that discharge distances predicted from launch speeds by Stokes' model provide a much better match to measured distances than estimates from the more complex drag model. Stokes' model works better over a wide range projectile sizes, launch speeds, and discharge distances, from microscopic mushroom ballistospores discharged at <1 m s(-1) over a distance of <0.1mm (Re<1.0), to macroscopic sporangia of Pilobolus that are launched at >10 m s(-1) and travel as far as 2.5m (Re>100).},
}

Fungi/*chemistry/cytology
Models, Biological
Spores, Fungal/*chemistry/cytology
Viscosity

@article {pmid20422105,
year = {2010},
author = {Xia, HM and Wang, ZP and Koh, YX and May, KT},
title = {A microfluidic mixer with self-excited 'turbulent' fluid motion for wide viscosity ratio applications.},
journal = {Lab on a chip},
volume = {10},
number = {13},
pages = {1712-1716},
doi = {10.1039/b925025e},
pmid = {20422105},
issn = {1473-0197},
abstract = {In micromixer studies, compared with the design, modeling and characterization, the influence of the fluid properties on mixing has been less discussed. This topic is of practical significance as the properties of diverse biological and chemical liquids to be mixed have large variations. Here, we report a microfluidic mixer for mixing fluids with widely different viscosities. It contains an interconnected multi-channel network through which the bulk fluid volumes are divided into smaller ones and chaotically reorganized. Then, the multiple fluid streams are driven into an expansion chamber which triggers viscous flow instabilities. Experiments with the co-flow of glycerol and aqueous solutions show an automatic transition of the flow from a steady state to a 'turbulent' state, significantly enhancing the mixing. This observation is rather interesting considering that it occurs in a passive flow and the average Reynolds number involved is small. Further testing indicates that this mixer works well at viscosity ratio (chi) up to the order of 10(4).},
}

@article {pmid18553503,
year = {2008},
author = {Venkiteshwaran, A and Heider, P and Teysseyre, L and Belfort, G},
title = {Selective precipitation-assisted recovery of immunoglobulins from bovine serum using controlled-fouling crossflow membrane microfiltration.},
journal = {Biotechnology and bioengineering},
volume = {101},
number = {5},
pages = {957-966},
doi = {10.1002/bit.21964},
pmid = {18553503},
issn = {1097-0290},
mesh = {Adsorption ; Ammonium Sulfate/chemistry ; Animals ; Biotechnology/methods ; Cattle ; Fractional Precipitation ; Immunoglobulins/*analysis/chemistry ; Serum/chemistry ; Serum Albumin, Bovine/analysis/chemistry ; Ultrafiltration/*methods ; },
abstract = {Efficient and economic recovery of immunoglobulins (Igs) from complex biological fluids such as serum, cell culture supernatant or fermentation cell lysate or supernatant, represents a substantial challenge in biotechnology. Methods such as protein A affinity chromatography and anion exchange chromatography are limited by cost and selectivity, respectively, while membrane chromatography is limited by low adsorptive area, flow distribution problems and scale-up difficulties. By combining the traditional salt-assisted precipitation process for selective removal of Igs from serum followed by constant-permeate flux membrane microfiltration for low fouling, we demonstrate an exciting new, efficient and economic hybrid method. The high selectivity of an ammonium sulfate-induced precipitation step was used to precipitate the Igs leaving the major undesirable impurity, the bovine serum albumin (BSA), in solution. Crossflow membrane microfiltration in diafiltration mode was then employed to retain the precipitate, while using axial flow rates to optimize removal of residual soluble BSA to the permeate. The selectivity between immunoglobulin G (IgG) and BSA obtained from the precipitation step was approximately 36, with 97% removal of the BSA with diafiltration in 5 diavolumes with resulting purity of the IgG of approximately 93% after the membrane microfiltration step. Complete resolubilization of the IgG was obtained without any aggregation at the concentrations of ammonium sulfate employed in this work. Further, membrane pore size and axial Reynolds number (recirculation rate) were shown to be important for minimizing fouling and loss of protein precipitate.},
}

Adsorption
Ammonium Sulfate/chemistry
Animals
Biotechnology/methods
Cattle
Fractional Precipitation
Immunoglobulins/*analysis/chemistry
Serum/chemistry
Serum Albumin, Bovine/analysis/chemistry
Ultrafiltration/*methods

@article {pmid18517526,
year = {2008},
author = {Malik, M and Dey, J and Alam, M},
title = {Linear stability, transient energy growth, and the role of viscosity stratification in compressible plane Couette flow.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {77},
number = {3 Pt 2},
pages = {036322},
doi = {10.1103/PhysRevE.77.036322},
pmid = {18517526},
issn = {1539-3755},
abstract = {Linear stability and the nonmodal transient energy growth in compressible plane Couette flow are investigated for two prototype mean flows: (a) the uniform shear flow with constant viscosity, and (b) the nonuniform shear flow with stratified viscosity. Both mean flows are linearly unstable for a range of supersonic Mach numbers (M). For a given M , the critical Reynolds number (Re) is significantly smaller for the uniform shear flow than its nonuniform shear counterpart; for a given Re, the dominant instability (over all streamwise wave numbers, alpha) of each mean flow belongs to different modes for a range of supersonic M . An analysis of perturbation energy reveals that the instability is primarily caused by an excess transfer of energy from mean flow to perturbations. It is shown that the energy transfer from mean flow occurs close to the moving top wall for "mode I" instability, whereas it occurs in the bulk of the flow domain for "mode II." For the nonmodal transient growth analysis, it is shown that the maximum temporal amplification of perturbation energy, G(max), and the corresponding time scale are significantly larger for the uniform shear case compared to those for its nonuniform counterpart. For alpha=0 , the linear stability operator can be partitioned into L ~ L+Re(2) L(p), and the Re-dependent operator L(p) is shown to have a negligibly small contribution to perturbation energy which is responsible for the validity of the well-known quadratic-scaling law in uniform shear flow: G(t/Re) ~ Re(2). In contrast, the dominance of L(p) is responsible for the invalidity of this scaling law in nonuniform shear flow. An inviscid reduced model, based on Ellingsen-Palm-type solution, has been shown to capture all salient features of transient energy growth of full viscous problem. For both modal and nonmodal instability, it is shown that the viscosity stratification of the underlying mean flow would lead to a delayed transition in compressible Couette flow.},
}

@article {pmid17014140,
year = {2006},
author = {Matteucci, ME and Hotze, MA and Johnston, KP and Williams, RO},
title = {Drug nanoparticles by antisolvent precipitation: mixing energy versus surfactant stabilization.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {22},
number = {21},
pages = {8951-8959},
doi = {10.1021/la061122t},
pmid = {17014140},
issn = {0743-7463},
mesh = {Itraconazole/*chemistry ; Microscopy, Electron, Scanning ; Nanoparticles/*chemistry/*ultrastructure ; Particle Size ; Solvents/*chemistry ; Surface-Active Agents/*chemistry ; Temperature ; },
abstract = {Organic itraconazole (ITZ) solutions were mixed with aqueous solutions to precipitate sub-300 nm particles over a wide range of energy dissipation rates, even for drug loadings as high as 86% (ITZ weight/total weight). The small particle sizes were produced with the stabilizer poloxamer 407, which lowered the interfacial tension, increasing the nucleation rate while inhibiting growth by coagulation and condensation. The highest nucleation rates and slowest growth rates were found at temperatures below 20 degrees C and increased with surfactant concentration and Reynolds number (Re). This increase in the time scale for growth reduced the Damkohler number (Da) (mixing time/precipitation time) to low values even for modest mixing energies. As the stabilizer concentration increased, the average particle size decreased and reached a threshold where Da may be considered to be unity. Da was maintained at a low value by compensating for a change in one variable away from optimum conditions (for small particles) by manipulating another variable. This tradeoff in compensation variables was demonstrated for organic flow rate vs Re, Re vs stabilizer concentration, stabilizer feed location (organic phase vs aqueous phase) vs stabilizer concentration, and stabilizer feed location vs Re. A decrease in the nucleation rate with particle density in the aqueous suspension indicated that secondary nucleation was minimal. A fundamental understanding of particle size control in antisolvent precipitation is beneficial for designing mixing systems and surfactant stabilizers for forming nanoparticles of poorly water soluble drugs with the potential for high dissolution rates.},
}

Itraconazole/*chemistry
Microscopy, Electron, Scanning
Nanoparticles/*chemistry/*ultrastructure
Particle Size
Solvents/*chemistry
Surface-Active Agents/*chemistry
Temperature

@article {pmid16919667,
year = {2006},
author = {Khair, AS},
title = {The 'Einstein correction' to the bulk viscosity in n dimensions.},
journal = {Journal of colloid and interface science},
volume = {302},
number = {2},
pages = {702-703},
doi = {10.1016/j.jcis.2006.07.076},
pmid = {16919667},
issn = {0021-9797},
abstract = {We calculate the effective bulk viscosity of a dilute dispersion of rigid n-dimensional hyperspheres in a compressible Newtonian fluid at zero Reynolds number.},
}

@article {pmid16907217,
year = {2006},
author = {Lishchuk, SV and Halliday, I and Care, CM},
title = {Shear viscosity of bulk suspensions at low Reynolds number with the three-dimensional lattice Boltzmann method.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {74},
number = {1 Pt 2},
pages = {017701},
doi = {10.1103/PhysRevE.74.017701},
pmid = {16907217},
issn = {1539-3755},
abstract = {We report three-dimensional parallel Lagrangian particle simulations using the lattice Boltzmann method, conducted at a low Reynolds number. Using modified Lees-Edwards boundary conditions and directly calculated viscous dissipation, we show that it is possible to recover excellent agreement with the Einstein viscosity formula in the low concentration limit and to predict viscosity corrections for larger concentrations.},
}

@article {pmid15447583,
year = {2004},
author = {Cohen, I},
title = {Scaling and transition structure dependence on the fluid viscosity ratio in the selective withdrawal transition.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {70},
number = {2 Pt 2},
pages = {026302},
doi = {10.1103/PhysRevE.70.026302},
pmid = {15447583},
issn = {1539-3755},
abstract = {In the selective withdrawal experiment, fluid is withdrawn through a tube with its tip suspended above a two-fluid interface. At sufficiently high flow rates, the interface undergoes a transition so that the lower fluid is entrained with the upper one, forming a spout. Previous experiments address the scalings and similarity profiles characterizing steady states of the system near the transition for one combination of fluids. In the present study, we show that these scalings and similarity profiles extend to systems with different viscosity ratios. Surprisingly, we find no dependence of the scalings and similarity profiles on the lower fluid viscosity. We use the results of a low-Reynolds-number flow dimensional analysis to show that for different fluid combinations the curves denoting the transition straw height as a function of flow rate can be collapsed. Finally, these results are used to argue that in the low-Reynolds-number regime, the capillary length sets the scale for the final curvature of the interface before the transition.},
}

@article {pmid14754200,
year = {2003},
author = {Raiskinmäki, P and Aström, JA and Kataja, M and Latva-Kokko, M and Koponen, A and Jäsberg, A and Shakib-Manesh, A and Timonen, J},
title = {Clustering and viscosity in a shear flow of a particulate suspension.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {68},
number = {6 Pt 1},
pages = {061403},
doi = {10.1103/PhysRevE.68.061403},
pmid = {14754200},
issn = {1539-3755},
abstract = {A shear flow of particulate suspension is analyzed for the qualitative effect of particle clustering on viscosity using a simple kinetic clustering model and direct numerical simulations. The clusters formed in a Couette flow can be divided into rotating chainlike clusters and layers of particles at the channel walls. The size distribution of the rotating clusters is scale invariant in the small-cluster regime and decreases rapidly above a characteristic length scale that diverges at a jamming transition. The behavior of the suspension can qualitatively be divided into three regimes. For particle Reynolds number Re(p) less than or approximately equal 0.1, viscosity is controlled by the characteristic cluster size deduced from the kinetic clustering model. For Re(p) approximately 1, clustering is maximal, but the simple kinetic model becomes inapplicable presumably due to onset of instabilities. In this transition regime viscosity begins to increase. For Re(p) greater than or approximately equal 10, inertial effects become important, clusters begin to breakup, and suspension displays shear thickening. This phenomenon may be attributed to enhanced contribution of solid phase in the total shear stress.},
}

@article {pmid14683081,
year = {2003},
author = {Zhang, YT and Shi, J and Shu, CW and Zhou, Y},
title = {Numerical viscosity and resolution of high-order weighted essentially nonoscillatory schemes for compressible flows with high Reynolds numbers.},
journal = {Physical review. E, Statistical, nonlinear, and soft matter physics},
volume = {68},
number = {4 Pt 2},
pages = {046709},
doi = {10.1103/PhysRevE.68.046709},
pmid = {14683081},
issn = {1539-3755},
abstract = {A quantitative study is carried out in this paper to investigate the size of numerical viscosities and the resolution power of high-order weighted essentially nonoscillatory (WENO) schemes for solving one- and two-dimensional Navier-Stokes equations for compressible gas dynamics with high Reynolds numbers. A one-dimensional shock tube problem, a one-dimensional example with parameters motivated by supernova and laser experiments, and a two-dimensional Rayleigh-Taylor instability problem are used as numerical test problems. For the two-dimensional Rayleigh-Taylor instability problem, or similar problems with small-scale structures, the details of the small structures are determined by the physical viscosity (therefore, the Reynolds number) in the Navier-Stokes equations. Thus, to obtain faithful resolution to these small-scale structures, the numerical viscosity inherent in the scheme must be small enough so that the physical viscosity dominates. A careful mesh refinement study is performed to capture the threshold mesh for full resolution, for specific Reynolds numbers, when WENO schemes of different orders of accuracy are used. It is demonstrated that high-order WENO schemes are more CPU time efficient to reach the same resolution, both for the one-dimensional and two-dimensional test problems.},
}

@article {pmid12141363,
year = {2002},
author = {Ginsberg, JH},
title = {On the effect of viscosity in scattering from partially coated infinite cylinders.},
journal = {The Journal of the Acoustical Society of America},
volume = {112},
number = {1},
pages = {46-54},
doi = {10.1121/1.1479147},
pmid = {12141363},
issn = {0001-4966},
abstract = {This paper considers the two-dimensional problem of scattering of a plane wave incident on an infinite cylinder that is coated with strips of pressure-release material extending over quadrants on the illuminated and shadowed sides, with the remainder of the surface considered to be rigid. Transitions from soft to rigid surfaces correspond to discontinuous boundary conditions. Ideal fluid theory predicts an infinite pressure gradient at these transitions, which suggests that viscous effects may be significant. The present work is a quantitative analysis of the global effect on acoustic scattering of viscosity effects arising in the vicinity of the discontinuity. The analysis represents the scattered field in terms of acoustic and vortical contributions. Both contributions are represented by series expansions in terms of azimuthal harmonics and associated cylindrical wave functions. The amplitudes of these harmonics are determined by satisfying a pair of discontinuous boundary conditions. Results obtained by using the method of weighted residuals are shown to be less accurate than those obtained from a collocation procedure. The results for surface pressure and farfield directivity indicate that viscous effects are important only if the Reynolds number is extremely small.},
}

@article {pmid11254273,
year = {2000},
author = {Pal, R},
title = {Shear Viscosity Behavior of Emulsions of Two Immiscible Liquids.},
journal = {Journal of colloid and interface science},
volume = {225},
number = {2},
pages = {359-366},
doi = {10.1006/jcis.2000.6776},
pmid = {11254273},
issn = {1095-7103},
abstract = {The viscous behavior of oil-in-water (O/W) emulsions is studied over a broad range of dispersed-phase concentrations (φ) using a controlled-stress rheometer. At low-to-moderate values of φ (φ<0.60), emulsions exhibit Newtonian behavior. The droplet size does not exert any influence on the viscosity of Newtonian emulsions. However, at higher values of φ, emulsions exhibit shear-thinning behavior. The viscosity of shear-thinning emulsions is strongly influenced by the droplet size; a significant increase in the viscosity occurs when the droplet size is reduced. With the decrease in droplet size, the degree of shear thinning in concentrated emulsions is also enhanced. The viscosity data of Newtonian emulsions are described reasonably well by the cell model of Yaron and Gal-Or (Rheol. Acta 11, 241 (1972)), which takes into account the effects of the dispersed-phase concentration as well as the viscosity ratio of the dispersed phase to continuous phase. The relative viscosities of non-Newtonian emulsions having different droplet sizes but the same dispersed-phase concentration are scaled with the particle Reynolds number. The high shear viscosities of non-Newtonian emulsions can be predicted fairly well by the cell model of Yaron and Gal-Or (Rheol. Acta 11, 241 (1972)). Copyright 2000 Academic Press.},
}

@article {pmid10656051,
year = {1998},
author = {Helmke, BP and Sugihara-Seki, M and Skalak, R and Schmid-Schönbein, GW},
title = {A mechanism for erythrocyte-mediated elevation of apparent viscosity by leukocytes in vivo without adhesion to the endothelium.},
journal = {Biorheology},
volume = {35},
number = {6},
pages = {437-448},
doi = {10.1016/s0006-355x(99)80021-3},
pmid = {10656051},
issn = {0006-355X},
mesh = {Animals ; Blood Viscosity/*physiology ; Capillaries ; *Endothelium, Vascular ; Erythrocytes/*physiology ; Leukocytes/*physiology ; Male ; Models, Biological ; Muscle, Skeletal/blood supply ; Perfusion ; Rats ; Rats, Wistar ; },
abstract = {In spite of the relatively small number of leukocytes in the circulation, they have a significant influence on the perfusion of such organs as skeletal muscle or kidney. However, the underlying mechanisms are incompletely understood. In the current study a combined in vivo and computational approach is presented in which the interaction of individual freely flowing leukocytes with erythrocytes and its effect on apparent blood viscosity are explored. The skeletal muscle microcirculation was perfused with different cell suspensions with and without leukocytes or erythrocytes. We examined a three-dimensional numerical model of low Reynolds number flow in a capillary with a train of erythrocytes (small spheres) in off-axis positions and single larger leukocytes in axisymmetric positions. The results indicate that in order to match the slower axial velocity of leukocytes in capillaries, erythrocytes need to position themselves into an off-axis position in the capillary. In such off-axis positions at constant mean capillary velocity, erythrocyte axial velocity matches on average the axial velocity of the leukocytes, but the apparent viscosity is elevated, in agreement with the whole organ perfusion observations. Thus, leukocytes influence the whole organ resistance in skeletal muscle to a significant degree only in the presence of erythrocytes.},
}

Animals
Blood Viscosity/*physiology
Capillaries
*Endothelium, Vascular
Erythrocytes/*physiology
Leukocytes/*physiology
Male
Models, Biological
Muscle, Skeletal/blood supply
Perfusion
Rats
Rats, Wistar

@article {pmid11607688,
year = {1996},
author = {Barenblatt, GI and Chorin, AJ},
title = {Small viscosity asymptotics for the inertial range of local structure and for the wall region of wall-bounded turbulent shear flow.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {93},
number = {13},
pages = {6749-6752},
doi = {10.1073/pnas.93.13.6749},
pmid = {11607688},
issn = {0027-8424},
abstract = {The small viscosity asymptotics of the inertial range of local structure and of the wall region in wallbounded turbulent shear flow are compared. The comparison leads to a sharpening of the dichotomy between Reynolds number dependent scaling (power-type) laws and the universal Reynolds number independent logarithmic law in wall turbulence. It further leads to a quantitative prediction of an essential difference between them, which is confirmed by the results of a recent experimental investigation. These results lend support to recent work on the zero viscosity limit of the inertial range in turbulence.},
}

@article {pmid1932716,
year = {1991},
author = {Cho, YI and Kensey, KR},
title = {Effects of the non-Newtonian viscosity of blood on flows in a diseased arterial vessel. Part 1: Steady flows.},
journal = {Biorheology},
volume = {28},
number = {3-4},
pages = {241-262},
doi = {10.3233/bir-1991-283-415},
pmid = {1932716},
issn = {0006-355X},
mesh = {Biomechanical Phenomena ; Blood Pressure/physiology ; Blood Viscosity/*physiology ; Coronary Disease/*pathology ; Coronary Vessels/*pathology ; Humans ; Models, Biological ; Regional Blood Flow ; },
abstract = {Effects of the non-Newtonian viscosity of blood on a flow in a coronary arterial casting of man were studied numerically using a finite element method. Various constitutive models were examined to model the non-Newtonian viscosity of blood and their model constants were summarized. A method to incorporate the non-Newtonian viscosity of blood was introduced so that the viscosity could be calculated locally. The pressure drop, wall shear stress and velocity profiles for the case of blood viscosity were compared for the case of Newtonian viscosity (0.0345 poise). The effect of the non-Newtonian viscosity of blood on the overall pressure drop across the arterial casting was found to be significant at a flow of the Reynolds number of 100 or less. Also in the region of flow separation or recirculation, the non-Newtonian viscosity of blood yields larger wall shear stress than the Newtonian case. The origin of the non-Newtonian viscosity of blood was discussed in relation to the viscoelasticity and yield stress of blood.},
}

Biomechanical Phenomena
Blood Pressure/physiology
Blood Viscosity/*physiology
Coronary Disease/*pathology
Coronary Vessels/*pathology
Humans
Models, Biological
Regional Blood Flow

@article {pmid3561030,
year = {1986},
author = {Chandran, KB and Fatemi, R and Schoephoerster, R},
title = {Dependence of tissue valve leaflet motion on the viscosity of blood analogue fluid.},
journal = {Life support systems : the journal of the European Society for Artificial Organs},
volume = {4},
number = {4},
pages = {289-303},
pmid = {3561030},
issn = {0261-989X},
mesh = {Animals ; *Bioprosthesis ; Blood Pressure ; *Blood Viscosity ; Glycerol ; Heart Rate ; *Heart Valve Prosthesis ; Heart Valves/*physiology ; Image Processing, Computer-Assisted ; Models, Cardiovascular ; Movement ; Prosthesis Design ; Saline Solution, Hypertonic ; Swine ; },
abstract = {The dependence of the leaflet motion of bioprosthetic heart valves on the viscosity of the blood analogue fluid was studied in this work. A pericardial and a porcine tissue valve were mounted in a pulse duplicator and high-speed films were taken to record the motion of the valve leaflets. The blood analogue fluids used were physiological saline with a viscosity coefficient of 1.0 cP, and glycerol solution with a viscosity of 3.5 cP. The transvalvular pressure drop and percentage of regurgitation were also measured with the time-averaged flow rate maintained at 6.00 +/- 0.05 litres/min. Our results show that the leaflets did not stiffen with up to 15 days' exposure to glycerol. Also, there was no substantial difference in the time of opening of the leaflets or in the area of opening of the valves with the two blood analogue fluids. However, the leaflets closed substantially later in the cardiac cycle in the case of glycerol solution, owing to the interaction between the leaflets and the viscosity of the fluid. For proper comparison of the flow dynamics past prosthetic valves at comparable Reynolds number and Womersley number, our results suggest that glycerol solution should be used as the blood analogue fluid for tissue valves also.},
}

Animals
*Bioprosthesis
Blood Pressure
*Blood Viscosity
Glycerol
Heart Rate
*Heart Valve Prosthesis
Heart Valves/*physiology
Image Processing, Computer-Assisted
Models, Cardiovascular
Movement
Prosthesis Design
Saline Solution, Hypertonic
Swine

@article {pmid40775244,
year = {2025},
author = {Bhattacharyya, S and Al Taisan, N and Khatri, S and Souayeh, B and Alfannakh, H and Vishwakarma, DK},
title = {Magneto-hydrodynamic behavior of magnetic nanofluids in mini-channel heat sinks for electronics cooling.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {28861},
pmid = {40775244},
issn = {2045-2322},
abstract = {The rapid advancement of high-density electronic devices and data centres has heightened the demand for effective thermal management solutions capable of handling elevated heat fluxes within compact domains. Conventional cooling techniques often fail to meet these requirements efficiently. This study presents a numerical investigation of heat transfer enhancement in a mini-channel heat sink through the combined use of passive vortex generators (ribs) and externally applied magnetic fields. A two-dimensional simulation was conducted for a 40 mm × 4 mm mini-channel employing a 2% Fe3O4-water nanofluid, with magnets positioned at X = 15 mm and X = 25 mm to generate non-uniform magnetic fields ranging from 800 to 2000 G. Three rib configurations parallel, staggered, and ribbed were evaluated across a Reynolds number range of 50, 75, 100, 150, 180, and 210. Results indicate that the ribbed configuration provides the highest heat transfer improvement, achieving up to a 65% increase relative to the baseline, while the parallel arrangement attained the highest absolute Nusselt number. The friction factor increased with stronger magnetic fields but decreased with higher Reynolds numbers. The thermal enhancement factor remained consistently above unity, with peak values of 2.06 for ribbed, 1.77 for parallel, and 1.52 for staggered layouts. Overall, this study demonstrates that integrating rib-induced vortex generation with magnetic field effects offers a promising strategy for enhancing the thermal performance of mini-channel heat sinks, addressing the cooling demands of next-generation electronic and data centre applications.},
}

@article {pmid40772695,
year = {2025},
author = {Wang, Y and Berx, J},
title = {Braided mixing in confined chiral active matter.},
journal = {Soft matter},
volume = {},
number = {},
pages = {},
doi = {10.1039/d5sm00484e},
pmid = {40772695},
issn = {1744-6848},
abstract = {Efficient mixing of fluids is essential in many practical applications to achieve homogeneity. For microscopic systems, however, both diffusion and turbulence are ineffective methods to achieve chaotic mixing due to the low Reynolds number, hence either active stirring or inducing turbulence through geometric boundary effects are generally implemented. Here, we study a modified chiral Vicsek model, where active microswimmers act as moving rods, stirring the surrounding substrate. We study the degree of mixing in the patterns formed by interplay between confinement, chiral motion and alignment interactions. This mixing is computed by considering the entanglement of spacetime trajectories of the particles, which forms a braid. Optimising the finite-time braiding exponent of this braid then yields a set of constituent parameters of the system, showing that a pattern consisting of a local stable vortex droplet and an ordered oscillating phase achieves the highest degree of mixing.},
}

@article {pmid40763644,
year = {2025},
author = {Zheng, G and Nguyen, AV and Nguyen, TAH and Nguyen, NN and Ma, L},
title = {Advancing models of bubble-particle contact times: A comprehensive review of flotation attachment efficiency prediction.},
journal = {Advances in colloid and interface science},
volume = {345},
number = {},
pages = {103609},
doi = {10.1016/j.cis.2025.103609},
pmid = {40763644},
issn = {1873-3727},
abstract = {Bubble-particle attachment is a fundamental process in flotation, critical for determining separation efficiency, based on surface hydrophobicity and many other aspects of colloid and surface chemistry. This review examines and refines models of contact time - encompassing collision, sliding, and attachment interactions - to quantify attachment efficiency in flotation systems. It begins by exploring the underlying colloidal physics of bubble-particle collision and sliding interactions during attachment, emphasising the velocity components of particles at bubble surfaces, including water flow and particle settling. Approximate models for water velocity near bubble surfaces are critically assessed, considering the influence of gas holdup and bubble surface mobility. The review also evaluates sliding time models, addressing their role in predicting attachment efficiency under varying conditions, such as changes in Reynolds number, bubble surface mobility, flow asymmetry, gas holdup, and inertial forces. Experimental validation of these models is discussed, highlighting key insights into how water flow fields at the bubble surface and particle dynamics influence attachment processes. While interfacial interactions, microhydrodynamics, and particle morphology are not directly reviewed, this paper identifies them as critical factors to consider in future modelling efforts. By synthesising current models and emphasising areas for further development, this review advances understanding of bubble-particle attachment mechanisms and provides a foundation for optimising flotation efficiency through improved analytical and computational approaches.},
}

@article {pmid40761490,
year = {2025},
author = {Ebadi, A and Fanaei, AR and Hassanpour, A and Rostampour, V},
title = {A Numerical-Experimental Assessment of the Dilute Phase and Erosion in a Larvae-Killing Processing System: Considering the Geometry Variation.},
journal = {Food science & nutrition},
volume = {13},
number = {8},
pages = {e70771},
pmid = {40761490},
issn = {2048-7177},
abstract = {In the present study, the pneumatic conveying of wheat in the dilute phase focused on four different pipe cross-section ratios including a/b = 1.5, a/b = 2, b/a = 1.5, and b/a = 2 has been experimentally and numerically examined. The system consists of the conveying pipe used inside the larvae system, which is used to transfer materials. Due to the Reynolds number calculations, the conveying is conducted in the turbulent regime. The combination of Reynolds Stress and Discrete phase models (RSM-DPM) was used to model the fluid and solid phases, respectively. The dimensionless velocity magnitude, static and dynamic pressures, erosion, vorticity magnitude, and turbulence intensity contours were investigated in the four mentioned scenarios using ANSYS Fluent commercial software. According to the results, the inner radius of the elbows, and especially the first elbow, were the areas where the maximum velocity was observed in these sections. As a negative parameter, the maximum pressure drop was obtained with a value of 322 Pa at the cross-section ratio of a/b = 2, which made the selection of this ratio a great challenge. Also, the maximum erosion rate occurred at the cross-section ratio of a/b = 2, which is considered a negative parameter. Moreover, due to the rotational flows created in the inlet ratios b/a = 1.5 and b/a = 2, these ratios are not very practical in terms of application and will cause energy loss in the system through the interaction between the various flows. Finally, considering all scenarios among the four cross-section ratios, the ratio of a/b = 1.5 was proposed as the most appropriate selection.},
}

@article {pmid40753300,
year = {2025},
author = {Alirahimi, S and Mohammadi Alashti, H and Jafari, A},
title = {Acoustic standing wave driven bubble dynamics in Oldroyd-B fluids using a semi analytical approach.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {28274},
pmid = {40753300},
issn = {2045-2322},
abstract = {Bubble oscillation plays a pivotal role in a multitude of medical and industrial applications. In this study, we employ a semi-analytical method to investigate the oscillation of a bubble in a viscoelastic fluid. The bubble is assumed to oscillate isothermally, and the well-known Rayleigh-Plesset equation for bubble dynamics is employed alongside the Oldroyd-B constitutive equation for the viscoelastic fluid. By applying the Leibniz integral rule, the governing integro-differential equation is converted into a system of four ordinary differential equations, which are then solved numerically. The results demonstrate that modifying each dimensionless parameter exerts a distinct influence on bubble oscillation, depending on the elasticity number and other parameters such as the amplitude of acoustic pressure. In the range of non-dimensional values under consideration, an increase in the Reynolds number, acoustic pressure, and acoustic frequency has been observed to exert a significant influence on the amplitude of bubble oscillation, relative to the influence of other parameters. As the Reynolds number approaches approximately 1.1, the bubble oscillations become chaotic. In contrast, at lower Reynolds numbers, the oscillations remain periodic. Moreover, our findings indicate that a Deborah number of 2.4 represents the most elastic fluid in which bubble oscillations were observed. When the elasticity number is approximately 10 or higher and the Reynolds number remains constant, further increases in elastic effects do not significantly impact the oscillations.},
}

@article {pmid40733761,
year = {2025},
author = {Li, H and Yu, X and Fu, Z and Lu, S},
title = {Stabilization mechanisms of foams enhanced by xanthan gum and sodium carboxymethyl cellulose: Rheology-bubble structure interplay and predictive criteria for drainage delays.},
journal = {Carbohydrate polymers},
volume = {366},
number = {},
pages = {123901},
doi = {10.1016/j.carbpol.2025.123901},
pmid = {40733761},
issn = {1879-1344},
abstract = {Investigating the stabilization mechanisms of foams is critical for diverse industrial applications. In this study, xanthan gum (XG) and sodium carboxymethyl cellulose (CMC) were employed to prepare foams. The results revealed that the expansion ratio was governed by the gas-liquid Reynolds number. When the liquid Reynolds number was less than 9, the expansion ratio was less than 5. The bubble diameter strongly depended on the liquid capillary number and the gas Reynolds number. For industries that need delicate foam, a high liquid capillary number and a high gas Reynolds number are needed. In addition, a linear relationship between the foam yield stress and bubble size was observed, along with a negative quadratic dependence on the expansion ratio. Furthermore, when the bubble diameter was less than the critical value (the foam yield stress exceeded the local stress within the plateau border), no liquid flowed out of the foam (drainage delay). A predictive model for the critical bubble diameter and delayed drainage time was developed (with a deviation of 25 % between the predicted and experimental values), incorporating zero-shear-rate viscosity, expansion ratio, and bubble size. This research provides theoretical guidance for the application of foam in different industrial scenarios.},
}

@article {pmid40715687,
year = {2025},
author = {Nzimande, SN and Sanusi, IA and Yobo, K and Ramchuran, SO and Kana, GEB},
title = {Process development for antifungal production by Bacillus subtilis BS20: nanoparticle supplementation, process optimization and preliminary scale-up studies.},
journal = {Bioprocess and biosystems engineering},
volume = {},
number = {},
pages = {},
pmid = {40715687},
issn = {1615-7605},
abstract = {The intensive agricultural practices used to meet global crop production demands have resulted in rigorous use of chemical pesticides. These ultimately compromise crop production as well as the environment. To alleviate these challenges, cheaper and environmentally friendly biocontrol agents have been considered as an alternative to chemical pesticides. Hence, this study was undertaken with the aim of enhancing antifungal production by Bacillus subtilis BS20 through process modeling, optimization, nanocatalysis and subsequent assessment of the scale up potential of the optimized process. The investigated process parameters included glucose concentration (10-30 g/L), incubation temperature (25-45 ℃) and incubation time (24-96 h). Optimized process conditions of 11.5 g/L glucose concentration, 24 h incubation time and 41 °C incubation temperature produced maximal antifungal activity of 68 mm zone of inhibition. Moreover, the inclusion of nanoparticles favored increased biomass yield but low antifungal activity. Additionally, constant power consumption, Reynolds number (Re) and impeller tip (Vtip) speed were implemented to scale up the antifungal production by B. subtilis BS20. Implementing constant Vtip value from the 1 L scale: 93 rpm, Re = 5.9E-04, Power (P) = 0.32 W, Power to Volume ratio (P/VL) = 160 W/m[3], circulation time (tc) = 5.2 s and shear stress (γ) = 15.5 S[-1], at 41 °C, gave the highest antifungal activity of 65 mm zone of inhibition in the 10 L scale bioreactor compared to the 1L bioreactors (57 mm). These findings have elucidated improved antifungal production by B. subtilis BS20 as well as provided a preliminary data for large scale production.},
}

@article {pmid40677126,
year = {2025},
author = {Bartol, IK and Ganley, AM and Krueger, PS and Thompson, JT},
title = {Squid paralarvae turn with high agility using jets near the Reynolds number threshold for viscous domination.},
journal = {The Journal of experimental biology},
volume = {},
number = {},
pages = {},
doi = {10.1242/jeb.250186},
pmid = {40677126},
issn = {1477-9145},
support = {1557669//Division of Integrative Organismal Systems/ ; 1557698//Division of Integrative Organismal Systems/ ; 1557838//Division of Integrative Organismal Systems/ ; },
abstract = {Turning is critical for survival in the ocean, as marine animals need to maneuver to capture prey, elude predators, and navigate complex environments. While prior research has focused on turning performance of adult swimmers, less is known about early ontogenetic stages that locomote within lower Reynolds number (Re) regimes, especially young jetters. To evaluate squid paralarval turning proficiency and the role of the pulsed jet in maneuvers, recently hatched longfin squid Doryteuthis pealeii swimming in a viewing chamber were studied using digital particle image velocimetry and kinematic motion analyses. Paralarvae exhibited a wide repertoire of turning behaviors, including those performed arms-first and tail-first. Paralarval turns were broader [higher mean length-specific turning radii (R/Lmean)] and faster [higher mean angular velocity (Ωmean)] than older squids, with some turns (∼8%) involving peak angular velocities (Ωmax)>2,000 deg s-1. Relative to cuttlefish hatchlings, squid paralarvae exhibited lower R/Lmeanand higher Ωmean and Ωmax. Higher angular jet impulse produced turns of greater Ωmean and total angular displacement, and R/Lmean and Ωmean increased with higher Resquid. Paralarval jets ranged from isolated vortex rings (short pulses), some of which occurred near the viscous dominated condition of Re<1, to elongated vorticity structures with and without leading edge vortex ring formation (long pulses). Despite the range of jet flows produced, strong relationships between jet length-to-diameter ratios and kinematic properties were not observed. The ability of paralarvae to produce a diversity of directed jets at low/intermediate Re is integral to their turning versatility and ultimately survival.},
}

@article {pmid40674327,
year = {2025},
author = {Bucha, MH and Khan, NB and Uddin, E and Riaz, HH and Munir, A and Farooq, U and Zhao, M and Muhammad, R and Jameel, M and Nasir, MT and Qadri, MNM},
title = {Experimental investigation of surface roughness effects on energy harvesting from a piezoelectric eel behind a cylindrical bluff body.},
journal = {PloS one},
volume = {20},
number = {7},
pages = {e0327916},
pmid = {40674327},
issn = {1932-6203},
mesh = {Animals ; Surface Properties ; *Eels/physiology ; *Renewable Energy ; Vibration ; },
abstract = {Due to dwindling energy reserves and the cost-effectiveness of installation, the global trajectory is shifting towards renewable energy sources as a proficient means of energy acquisition. Among these sources, hydropower stands out as it harnesses the kinetic energy of oceanic water flow to generate power. Various studies have harnessed vortex-induced vibrations (VIV) to generate power from a piezoelectric eel, showcasing the diverse applications of this technology. The present experimental study further explores this technology and investigates the effect of surface roughness of cylindrical bluff body on the energy harvested by piezoelectric eel using a low-speed water tunnel. The experiments were performed at four different roughness values (Ks/D) namely 2.21, 4.07, 9.85, and 13.97 microns for the cylinders with diameters of 25, 27, 27.2, and 27.5 mm, respectively. The Reynolds number in the present study is fixed at 8690. A total of hundred case studies were performed to analyze the effect of the surface roughness of the cylinder on energy harvesting performance from the eel. The flapping frequency, amplitude, and optimal power of the rough cylinders were analyzed and compared with that of smooth cylinders experimentally, and the optimum point ([Formula: see text]) in terms of power was attained. Increased surface roughness significantly reduced power output, flapping frequency, and amplitude. The smoothest cylinder (Ks/D = [Formula: see text]) produced the highest power (52.325 µW), while the roughest (Ks/D = [Formula: see text]) resulted in a 6.26% decrease in power (36.4 µW), along with reductions of 4.5% in flapping frequency and 20% in amplitude. By increasing the surface roughness of the bluff body, the lock-in region decreases and as a result, the harvested power from that bluff body is reduced. Moreover, the power also decreased by increasing the distance between the cylinder and eel both in the x- and y-direction. The results of the current study provide deeper insights into the effect of surface roughness on energy harvesting from piezoelectric eel behind cylindrical bluff body, that are essential for the development of efficient energy harvesting systems. The findings of this study would be useful for the design of piezoelectric eel-based energy harvesting devices in marine environments.},
}

Animals
Surface Properties
*Eels/physiology
*Renewable Energy
Vibration

@article {pmid40671595,
year = {2025},
author = {Hussain, MA and Gupta, R},
title = {Mass Transfer in Gas-Liquid Taylor Flow in Microchannels: Effect of Henry's Constant, Two-Phase Velocity, Bubble Length, and Slug Length.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {},
number = {},
pages = {},
doi = {10.1021/acs.langmuir.5c01549},
pmid = {40671595},
issn = {1520-5827},
abstract = {Microreactors offer the advantage of high interfacial area density and are, therefore, ideal candidates for performing gas-liquid reactions limited by the mass transfer between the two phases. The slug or Taylor flow regime is generally the preferred regime of operation due to its unique flow characteristics. In this work, we use the volume of fluid method to model mass transfer in gas-liquid Taylor flow in a circular microchannel and understand the effect of two-phase or mixture velocity, bubble length, slug length, and Henry's constant on mass transfer. The concentration field is computed in both phases, and the concentration jump across the gas-liquid interface is modeled in accordance with Henry's law using the Compressive Continuous Species Transfer method. The performance of the mass transfer process is reported in terms of the dimensionless mass transfer coefficient and Sherwood number. The Sherwood number is observed to initially increase with the Reynolds number and eventually reach a plateau, suggesting that stronger convection can enhance the mass transfer only to a certain extent. Increasing the bubble length resulted in a decrease in the Sherwood number despite an increase in specific area, whereas increasing the liquid slug length resulted in an increase in the Sherwood number despite a decrease in specific area. Furthermore, a decrease in Henry's constant resulted in a decrease in the Sherwood number, implying that the chemical species are sparingly soluble in the liquid phase compared to the gas phase.},
}

@article {pmid40671441,
year = {2025},
author = {Farzaneh, M and Zgheib, N and Balachandar, S and Sherif, SA},
title = {Numerical simulation of frost formation and heat transfer on fin-and-tube heat exchangers in turbulent cross-flow.},
journal = {Philosophical transactions. Series A, Mathematical, physical, and engineering sciences},
volume = {383},
number = {2301},
pages = {20240366},
pmid = {40671441},
issn = {1471-2962},
support = {//U.S. Department of Energy/ ; //Advanced Manufacturing Office/ ; },
abstract = {Frost formation in fin-and-tube heat exchangers in turbulent cross-flow presents significant challenges in industrial refrigeration applications, affecting heat transfer efficiency and operational reliability. The purpose of this work is to investigate frost deposition and growth on a staggered bank of a fin-and-tube freezer coil under turbulent forced convection conditions. The focus here is on investigating conditions that closely replicate real-world scenarios in large walk-in industrial freezers. Using a direct numerical simulation approach, we examine the flow dynamics and thermal behaviour in the presence of frost, considering turbulent regimes characterized by a Reynolds number in the range [Formula: see text], with the characteristic length being the outer diameter of the tube and the velocity being the bulk fluid velocity between the plates (fins). Computational fluid dynamics simulations are employed to resolve the interactions between turbulent airflow and the frost layer. Our approach incorporates a modified immersed boundary method and a slow-time acceleration technique to address the complex dynamic interface between the continuously evolving frost layer and the flowing air stream. Our findings indicate that frost forms more on the sides of the finned surfaces (plates) and less on the tubes themselves.This article is part of the theme issue 'Heat and mass transfer in frost and ice'.},
}

@article {pmid40670575,
year = {2025},
author = {Chandrakar, V and Bhattad, A and Samal, P and Senapati, JR and Kashyap, AK},
title = {A study on different methods to change the Rayleigh number in the analysis of heat transfer.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {25773},
doi = {10.1038/s41598-025-11120-9},
pmid = {40670575},
issn = {2045-2322},
abstract = {This study provides awareness about natural convection and associated non-dimensional numbers like the Prandtl number, Grashof number, Rayleigh number, and Reynolds number. The main focus of this research is to present the different methods employed to vary the Rayleigh number [Formula: see text] in an extensive range. The research concludes that changing the gravity value to obtain the considerable variation in [Formula: see text] is also a possible method for conducting the numerical analysis and observing the impact of the Rayleigh number. The validation of the numerical scheme with existing literature is provided here. An attempt is made to show that similar effects could be obtained by changing the value of gravity and the body's characteristics length. The comparative results obtained by changing length and gravity are presented which gives almost the same result [Formula: see text]error) to get the same [Formula: see text]. This presents the beauty of a non-dimensional study. Moreover, it is possible to say that in the non-dimensional analysis of engineering practice, the individual variables that are changed are not important considering the non-dimensional results.},
}

@article {pmid40670553,
year = {2025},
author = {Berger, T and Farhat, M},
title = {Gyroid as a novel approach to suppress vortex shedding and mitigate induced vibration.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {25777},
pmid = {40670553},
issn = {2045-2322},
support = {219723//Swiss National Science Fund/ ; },
abstract = {The present study uncovers how a Gyroid-structured extension, attached to a hydrofoil trailing edge, may prevent the formation of Karman vortices and remarkably reduce vortex-induced vibration (VIV). The case study is a blunt truncated NACA 0009 hydrofoil of 100 mm chord length and 150 mm span, placed in a water stream at high Reynolds number (Re = 0.6 × 10[6] to 2 × 10[6]). In the absence of the Gyroid extension, as the flow velocity is increased from 6 to 20 m/s, the alternate Karman vortices generated in the wake are responsible for the hydrofoil vibration with a strong torsional lock-in at flow velocities ranging from 15 to 17 m/s. The Gyroid extension, however, largely reduces the flow-induced vibrations and the lock-in is completely suppressed. Specifically, the RMS value of the surface velocity signal is cut by 67% under lock-off conditions and 99.5% under lock-in conditions. Detailed velocity measurements in the wake using laser Doppler velocimeter confirm that the Gyroid insert eliminates the frequency peak associated with the Strouhal shedding frequency and reduces broadband noise excitation. These measurements uncover how the combination of porosity and tortuosity of the Gyroid insert prevents the formation of coherent and periodic Karman vortices. In particular, we found that the Gyroid extension is responsible for the generation of streamwise and transverse jets, which extend into the far wake, inhibiting the roll-up of transient vortices in a remarkable way. We believe that this is the key mechanism in suppressing vortex shedding. Interestingly, the measurement of lift and drag forces did not reveal any significant alteration of the hydrodynamic performances of the hydrofoil with the Gyroid extension. These promising results have far-reaching implications for the design of mechanical structures subjected to VIV, such as aircraft wings, marine propellers, hydraulic pumps, and turbines among others. The potential benefits include reduced noise emissions and mitigated fatigue risks.},
}

@article {pmid40668908,
year = {2025},
author = {Drennan, WC and Aydin, O and Emon, B and Li, Z and Joy, MSH and Barishman, A and Kim, Y and Wei, M and Denham, D and Carrillo, A and Saif, MTA},
title = {A forward-engineered, muscle-driven soft robotic swimmer.},
journal = {Science advances},
volume = {11},
number = {29},
pages = {eadu8634},
pmid = {40668908},
issn = {2375-2548},
mesh = {*Robotics/instrumentation ; *Swimming/physiology ; Animals ; *Muscles/physiology ; Biomechanical Phenomena ; Muscle Contraction/physiology ; Motor Neurons/physiology ; },
abstract = {The field of biohybrid robotics focuses on using biological actuators to study the emergent properties of tissues and the locomotion of living organisms. On the basis of models of swimming at small size scales, we designed and fabricated a muscle-powered, flagellate swimmer. We investigate the design of a compliant mechanism based on nonlinear mechanics and its mechanical integration with a muscle ring and motor neurons. We find that within a range of anchor stiffnesses around 1 micronewton per micrometer, the homeostatic tension in muscle is insensitive to stiffness, offering greater design flexibility. The proximity of motor neurons results in a fourfold improvement in muscle contractility. Improved contractility and nonlinear design allow for a peak swimming speed about two orders of magnitude higher than previous biohybrid flagellate swimmers, reaching 0.58 body lengths per minute (86.8 micrometers per second), by a mechanism involving inertia that we verify through flow field imaging. This swimmer opens the door for a class of intermediate-Reynolds number swimmers.},
}

*Robotics/instrumentation
*Swimming/physiology
Animals
*Muscles/physiology
Biomechanical Phenomena
Muscle Contraction/physiology
Motor Neurons/physiology

@article {pmid40643328,
year = {2025},
author = {Bäuerlein, B and Avila, K},
title = {Pulsatile pipe flow experiment to study particle-fluid interactions using Lagrangian flow measurements.},
journal = {The Review of scientific instruments},
volume = {96},
number = {7},
pages = {},
doi = {10.1063/5.0254258},
pmid = {40643328},
issn = {1089-7623},
abstract = {Simultaneously tracking particle and fluid motion is notoriously challenging yet essential for experimentally elucidating their interaction dynamics. In this study, we present comprehensive three-dimensional measurements of particle-laden flow in a novel pipe flow experiment. The experimental setup features a pipe with a 28 mm diameter and a length of up to 20 m, capable of generating both steady and pulsatile flows using an accurately controlled piston-driven system. The Reynolds number range of 50-7400 allows exploration from laminar to turbulent flow regimes. Furthermore, the pulsatile flow capability enables investigations into the effects of driving frequency, amplitude, and waveform. The system's suitability for studying particle-laden flows with complex physiological pulsation waveforms is demonstrated in detail. Measurements employing three-dimensional Lagrangian particle tracking, based on the Shake-The-Box algorithm, illustrate the unprecedented potential of this method for in-depth analysis of spatiotemporally complex flows, as exemplified by particle-laden pulsatile pipe flow. For the first time, the flow field was tracked simultaneously with the dynamics of a hydrogel particle, capturing its position, velocity, rotational axis, and angular velocity. Such rich datasets can validate four-way coupling in multiphase flow simulations and provide critical insights into turbulence transitions induced by particles. Complementary measurement techniques are also presented, including an efficient single-camera setup to detect particle migration and high-resolution differential pressure measurements (with accuracy in the range of a few Pascals) to identify the onset of turbulence.},
}

@article {pmid40641610,
year = {2025},
author = {Chauhan, R and Usman, H and Minocha, N and Molaei, M and Niepa, THR and Singh, MR},
title = {Predictive Modeling and Experimental Validation of Magnetophoretic Delivery of Magnetic Nanocultures.},
journal = {ACS materials letters},
volume = {7},
number = {7},
pages = {2679-2685},
pmid = {40641610},
issn = {2639-4979},
abstract = {Magnetophoresis offers a powerful strategy for the targeted delivery of functional microcapsules. Here, we present a combined theoretical and experimental framework to predict the magnetophoretic transport of magnetic nanocultures-microcapsules embedded with magnetic nanoparticles and living cells. We derive a novel analytical expression for the terminal velocity of microcapsules under a spatially decaying magnetic field. The model incorporates magnetic and hydrodynamic forces in low Reynolds number regimes and predicts microcapsule velocity variations with nanoparticle size and field strength. Experimental validation using nanocultures containing nanoparticles 5, 10, and 20 nm in size confirms the model's accuracy, with 10-nm particles showing optimal magnetophoretic response. The model also accounts for hindered motion at high microcapsule densities. This work provides a predictive tool for designing magnetically guided systems for microbial delivery, localization, and patterning, with applications in bioreactors, therapy, and engineered living materials.},
}

@article {pmid40630703,
year = {2025},
author = {Li, D and Xing, J and Zhang, Z and Wang, H},
title = {Numerical investigation on the dynamic behavior of bubbles under forced flow in a microchannel.},
journal = {RSC advances},
volume = {15},
number = {29},
pages = {23414-23426},
pmid = {40630703},
issn = {2046-2069},
abstract = {Understanding the process of bubble detachment and motion along microchannel walls, driven by liquid flow, is crucial for elucidating bubble dynamics and realizing diverse applications within the realm of microfluidics. This paper uses the phase-field method to perform a comprehensive numerical study on the conversion of surface gas bubbles into bulk bubbles at the lower wall of a microfluidic channel. The study identifies several key factors that have a coupled impact on the 'surface-bulk' conversion, including wall wettability, Reynolds number, and the initial contact angle/volume of the surface bubbles (with contact angle and volume positively correlated at a fixed base radius). Specifically, higher Reynolds numbers, smaller initial bubble contact angles, and more hydrophilic channel walls facilitate the detachment of surface bubbles from the channel wall. However, at high Reynolds numbers, bubbles on superhydrophilic surfaces may be split, causing fluctuations or longer conversion time. Conversely, as wall hydrophobicity increases, surface bubbles remain attached.},
}

@article {pmid40623989,
year = {2025},
author = {Yazdanpanah Moghadam, E and Sonenberg, N and Packirisamy, M},
title = {Alzheimer model chip with microglia BV2 cells.},
journal = {Microsystems & nanoengineering},
volume = {11},
number = {1},
pages = {135},
pmid = {40623989},
issn = {2055-7434},
abstract = {Amyloid beta oligomers (AβO) are pivotal in Alzheimer's Disease (AD), cleared by microglia cells, as immune cells in the brain. Microglia cells exposed to AβO are involved with migration, apoptosis, phagocytosis, and activated microglial receptors through AβO, impacting cellular mechanobiological characteristics such as microglial adhesion strength to the underlying substrate. Herein, a label-free microfluidic device was used to detect advancing AD conditions with increasing AβO concentrations on microglia BV2 cells by quantitatively comparing the cell-substrate adhesion. The microfluidic device, acting as an AD model, comprises a single channel, which functions as a cell adhesion assay. To assess cell-substrate adhesion under different AβO concentrations of 1 µM, 2.5 µM, and 5 µM, the number of the cells attached to the substrate was counted by real-time microscopy when the cells were under the flow shear stress of 3 Pa and 7.5 Pa corresponding to Reynolds number (Re) of 10 and 25, respectively. The data showed that quantifying the cell-substrate adhesion using the microfluidic device could successfully identify conditions of advancing AβO concentrations. Our findings indicated that the increased incubation time with AβO caused reduced cell-substrate adhesion strength. Additionally, increased AβO concentration was another factor that weakened microglial interaction with the substrate. The quantification of cell-substrate adhesion using 3 Pa compared to 7.5 Pa clearly demonstrated advancing AβO in AD. This study using the chip provides an AD model for a deeper understanding mechanobiological behaviors of microglia exposed to AβO corresponding to diagnosed AD conditions under an in vitro microenvironment.},
}

@article {pmid40619480,
year = {2025},
author = {Donga, RK and Kumar, S and Velidi, G},
title = {Heat transfer enhancement in a parabolic trough collector using finned tubular absorber.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {24142},
pmid = {40619480},
issn = {2045-2322},
abstract = {This study presents an investigation into enhancing heat transfer in parabolic trough collectors (PTCs). The research focuses on improving convective heat transfer by incorporating longitudinal fins within the tubular absorber of a PTC. The study examines a PTC (parabolic trough collector) system with the following specifications: a 1.84 m focal length, a 5 m aperture width, and an absorber measuring 70 mm in outer diameter. The variable solar flux on the absorber is determined using SolTrace software. The receiver was simulated using the finite volume method. The heat flux derived from SolTrace simulations serves as a boundary condition. A comparative analysis is conducted between the findings from a parametric investigation on a standard receiver and those equipped with finned tubular absorbers. This comparison spans Reynolds numbers from 0.25 × 10[5] to 2.82 × 10[5]. Studies have demonstrated that absorbers with fins substantially improve heat transfer. The tubular absorber equipped with fins shows a significant rise of 40.1% in the Nusselt number. Its performance evaluation criteria reach a peak of 1.28 when the Reynolds number is 2.82 × 10[5].},
}

@article {pmid40609600,
year = {2025},
author = {Adak, R and Mandal, A and Saha, S},
title = {Direct numerical simulations of dragonfly-inspired corrugated tandem airfoils at low Reynolds number.},
journal = {Bioinspiration & biomimetics},
volume = {20},
number = {4},
pages = {},
doi = {10.1088/1748-3190/adebcf},
pmid = {40609600},
issn = {1748-3190},
mesh = {Animals ; *Wings, Animal/physiology/anatomy & histology ; *Flight, Animal/physiology ; Computer Simulation ; *Odonata/physiology/anatomy & histology ; *Models, Biological ; *Biomimetics/methods ; Biomechanical Phenomena ; },
abstract = {A corrugated wing is known to significantly enhance aerodynamic efficiency in the low Reynolds number regime. Although the result may be relatable directly to two-winged insects, larger insects flying at similar Reynolds numbers, like dragonflies, have four wings, and the role of the gap between the fore and hind wings in flight has rarely been analyzed. In particular, we perform direct numerical simulations of the flow past a tandem corrugated airfoil configuration at a chord Reynolds number of 10[4]that is of relevance to the micro-unmanned aerial vehicle (MAV) community. We assessed the tandem wing configuration for different horizontal and vertical offsets. In general, the aerodynamic efficiency for tandem configurations is quite high (∼ 10). Furthermore, we find that vertical offsets have a greater impact on aerodynamic forces than horizontal offsets. Positioning the hindwing below the forewing improves aerodynamic efficiency compared to placing the hindwing above because of the generation of a favorable pressure gradient on the forewing. The vortex shedding and correlations evaluate the hindwing/forewing interaction and the fluctuation of the forces. The horizontal offset results demonstrate improved aerodynamic efficiency and reduced flow unsteadiness as the gap between the two wings is minimized, primarily because the interaction between the forewing's wake and the hindwing is suppressed. A study with NACA 0008 is done to corroborate the range of optimal configurations and assess performance benefits of corrugated profile. In addition, the study reveals that the tandem wing configuration maintains efficiency comparable to that of a single wing, allowing us to utilize its advantages for MAV applications.},
}

Animals
*Wings, Animal/physiology/anatomy & histology
*Flight, Animal/physiology
Computer Simulation
*Odonata/physiology/anatomy & histology
*Models, Biological
*Biomimetics/methods
Biomechanical Phenomena

@article {pmid40608667,
year = {2025},
author = {Polanco, JI and Roche, PE and Danaila, L and Lévêque, E},
title = {Disentangling temperature and Reynolds number effects in quantum turbulence.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {122},
number = {27},
pages = {e2426598122},
pmid = {40608667},
issn = {1091-6490},
support = {ANR-18-CE46-0013 QUTE-HPC//Agence Nationale de la Recherche (ANR)/ ; },
abstract = {The interplay between viscous and frictional dissipation is key to understanding quantum turbulence dynamics in superfluid [4]He. Based on a coarse-grained two-fluid description, an original scale-by-scale energy budget that identifies each scale's contribution to energy dissipation is derived. Using the Hall-Vinen-Bekharevich-Khalatnikov (HVBK) model to further characterize mutual friction, direct numerical simulations at temperatures 1.44 K ≲ T ≲ 2.16 K indicate that mutual friction promotes intense momentum exchanges between the two fluids to maintain a joint energy cascade despite their viscosity mismatch. However, the resulting overall frictional dissipation remains small (compared to the viscous dissipation) and confined to far-dissipative scales. This remarkable feature allows us to define an effective Reynolds number for the turbulence intensity in a two-fluid system, helping to disentangle the effects of Reynolds number and temperature in quantum turbulence. Thereby, simple physical arguments predict that the distance ℓ between quantized vortices (normalized by the turbulence integral scale L0) should behave as [Formula: see text] with the Reynolds number based on the quantum of circulation κ. This law is well supported by a large set of experimental and numerical data within the temperature range of the HVBK model. Finally, this approach offers the possibility of revisiting the ongoing controversy on intermittency in quantum turbulence. It is shown that observed changes in intermittency arise from Reynolds number effects rather than from temperature variations, as proposed in recent studies.},
}

@article {pmid40603935,
year = {2025},
author = {Kazemi, M and Mani, M},
title = {Owl airfoil aerodynamic noise sources and performance compared to hawk and NACA0012 airfoils for low Reynolds applications.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {23261},
pmid = {40603935},
issn = {2045-2322},
abstract = {The investigation of low Reynolds number flows is crucial, particularly for applications such as wind turbines and small-scale UAVs. This study compares the owl airfoil with the NACA0012 and hawk airfoils through wind tunnel testing, utilizing pressure sensors and force balance to examine the aerodynamic noise sources and aerodynamic performance of the airfoils. A total of six airfoils were investigated at various Reynolds numbers from 44 × 10[3] to 160 × 10[3], considering the glide flight envelop for various owl species. Wind tunnel test results showed higher Cl and L/D ratio for the owl airfoil, outperforming the NACA0012 and hawk airfoils by up to 6.7% and 44.1%, respectively. This is attributed to the optimal camber of the owl airfoil compared to the two other airfoils, and its lower relative thickness too. This helps flight with this airfoil at lower AOA, which reduces noise. In addition, the stall angle for owl airfoil was ranging from 8° to 15° higher than NACA0012 airfoil, which stalled at 10°-11°, and higher than 6° to 12° hawk stall angle. This feature allowed owls to perform efficient flights in glide phase at lower AOA that minimized the main aerodynamic noise sources such as the separations and pressure fluctuations. Pressure measurements represented the initiation of LSB for the owl airfoil at around AOA = 6° to 10° at different Reynolds numbers, while the hawk airfoil shown the presence of LSB starting from AOA = 0°. A detailed analysis of the pressure fluctuations showed that the owl airfoil had fewer sources of aerodynamic noise, such as LSB, stall phenomena, and separated shear layers, on both its upper and lower surfaces, compared to other types of airfoils. Additionally, an analysis in the frequency domain showed that the amplitude of FFT for NACA0012 and hawk airfoil is generally higher compared with the owl airfoil. These findings shed light on the aerodynamic characteristics and noise generation mechanisms of owl airfoil for future research and design considerations.},
}

@article {pmid40572435,
year = {2025},
author = {Qiu, Y and Zhang, X and Hao, M and Yin, X and Zhou, M and Ma, S and Zhang, Y and Jiang, N and Xie, L and Yuan, X and Chang, H},
title = {Investigation of Efficient Mixing Enhancement in a Droplet Micromixer with Short Mixing Length at Low Reynolds Number.},
journal = {Micromachines},
volume = {16},
number = {6},
pages = {},
pmid = {40572435},
issn = {2072-666X},
support = {52205601//National Natural Science Foundation of China/ ; Hefei 230026//Deep Space Exploration Laboratory/ ; },
abstract = {Rapid mixing is widely prevalent in the field of microfluidics, encompassing applications such as biomedical diagnostics, drug delivery, chemical synthesis, and enzyme reactions. Mixing efficiency profoundly impacts the overall performance of these devices. However, at the micro-scale, the flow typically presents as laminar flow due to low Reynolds numbers, rendering rapid mixing challenging. Leveraging the vortices within a droplet of the Taylor flow and inducing chaotic convection within the droplet through serpentine channels can significantly enhance mixing efficiency. Based on this premise, we have developed a droplet micromixer that integrates the T-shaped channels required for generating Taylor flow and the serpentine channels required for inducing chaotic convection within the droplet. We determined the range of inlet liquid flow rate and gas pressure required to generate Taylor flow and conducted experimental investigations to examine the influence of the inlet conditions on droplet length, total flow rate, and mixing efficiency. Under conditions where channel dimensions and liquid flow rates are identical, Taylor flow achieves a nine-fold improvement in mixing efficiency compared to single-phase flow. At low Reynolds number (0.57 ≤ Re ≤ 1.05), the chip can achieve a 95% mixing efficiency within a 2 cm distance in just 0.5-0.8 s. The mixer proposed in this study offers the advantages of simplicity in manufacturing and ease of integration. It can be readily integrated into Lab-on-a-Chip devices to perform critical functions, including microfluidic switches, formation of nanocomposites, synthesis of oxides and adducts, velocity measurement, and supercritical fluid fractionation.},
}

@article {pmid40549011,
year = {2025},
author = {Harrison, A and Strychalski, W and Hamlet, C and Miller, L},
title = {Fluid Dynamics of Multiple Fast-Firing Extrusomes : Fast extrusomes.},
journal = {Bulletin of mathematical biology},
volume = {87},
number = {7},
pages = {100},
pmid = {40549011},
issn = {1522-9602},
support = {DMS-1937229//National Science Foundation/ ; IOS-2227068//National Science Foundation/ ; GM132008//Foundation for the National Institutes of Health/ ; },
mesh = {Animals ; Mathematical Concepts ; *Models, Biological ; Hydrodynamics ; *Organelles/physiology ; Dinoflagellida/physiology ; Computer Simulation ; Predatory Behavior/physiology ; Viscosity ; },
abstract = {The contact and puncturing of cells and organisms in fluid at microscales are difficult due to viscous-dominated effects and the interactions of boundary layers. This challenge can be overcome in part through the ultra-fast firing of organelles such as the nematocysts of jellyfish. Such super-fast extrusive organelles found in cnidarians, protists, and dinoflagellates are known as extrusomes. It has previously been shown that a single barb at the cellular microscale must be fired fast enough to reach the inertial regime to contact prey. The fluid physics of multiple-fired extrusomes has not been carefully studied, however. The simultaneous firing of extrusomes can be seen in nature, with one example being the dinoflagellate Nematodunium, where each nematocyst consists of a ring of parallel sub-capsules similar to a Gatling gun. In this paper, the immersed boundary method was used to numerically simulate the dynamics of one, two, and three barb-like structures that are accelerated and released towards a passive elastic prey in two dimensions. We considered the simultaneous release of all three barbs as well as a sequential release of the barbs. We also vary the Reynolds number of the simulation for several orders of magnitude to consider the biologically relevant range of extrusome firing, given that different organelles are fired at different speeds and that some extrusomes are fired in viscous mucus. For multiple barbs, we found that there is a nonmonotonic relationship between the distance between the top of the center barb and the prey and the Reynolds number when fired simultaneously. This is because the prey is not pushed out of the way by boundary effects at higher Reynolds numbers, while barbs at lower Reynolds numbers entrain more fluid and are carried farther. Furthermore, the center barbs at the highest Reynolds numbers always hit the prey and are robust to firing order and the spacing between barbs. Overall, our simple model shows that the extreme nonlinearity of the fluid at this scale results in nonmonotonic relationships between the distance to the prey and various parameters.},
}

Animals
Mathematical Concepts
*Models, Biological
Hydrodynamics
*Organelles/physiology
Dinoflagellida/physiology
Computer Simulation
Predatory Behavior/physiology
Viscosity

@article {pmid40534053,
year = {2025},
author = {Ramirez, FR and Diamond, PH},
title = {Layered patterns of active scalar fields in a two-dimensional magnetohydrodynamic system.},
journal = {Physical review. E},
volume = {111},
number = {5-2},
pages = {055107},
doi = {10.1103/PhysRevE.111.055107},
pmid = {40534053},
issn = {2470-0053},
abstract = {We observe the formation of staircase patterns in the magnetic potential (A) in a weakly magnetized two-dimensional magnetohydrodynamic system driven by a forced, fluctuating vortex array. Layering occurs due to inhomogeneous mixing of A by vortex cells. Magnetic Reynolds number (R_{m})
-dependent quenching of the turbulent diffusion of A by weak magnetic fields increases the disparity between the (short) cell circulation time and the (long) time for intercell transport of magnetic potential. Thus, magnetic fields strengthen transport barriers between cells and reinforce the staircase, relative to its passive scalar counterpart. The analysis reveals a feedback mechanism, which promotes staircase formation. Magnetic staircases persist in both the flux expulsion (R_{m}v
_{A}^
{2}/
U_{0}^
{2}<
1) and vortex disruption (R_{m}v
_{A}^
{2}/
U_{0}^
{2}�
��1) limits. In the latter case, residual vortex cells homogenize A. Global layering morphology is shown to be well characterized by staircase curvature. Stochastic forcing of magnetic potential can support magnetic staircases against resistive decay.},
}

@article {pmid40533935,
year = {2025},
author = {Baños, R and Méndez, F and Bautista, O and Arcos, J},
title = {Spreading of a diffusive soluble surfactant in a deep layer with inertial effects.},
journal = {Physical review. E},
volume = {111},
number = {5-2},
pages = {055501},
doi = {10.1103/PhysRevE.111.055501},
pmid = {40533935},
issn = {2470-0053},
abstract = {In this study, we conduct a numerical analysis of the spreading dynamics of a soluble and diffusive surfactant in a deep layer of Newtonian fluid. We investigate three different initial conditions for the surfactant distributions: a Gaussian pulse, a Cauchy hole, and a periodic distribution. We solved the momentum equations in the Stokes limit (Re→0) and also considering inertial effects (Re≫1), where Re denotes the Reynolds number. Furthermore, we include the convective-diffusion equation for both nondiffusive (Pe_{s}
and Pe→∞) and diffusive (finite Pe_{s}
and Pe) surfactants, with Pe_{s}
and Pe representing surface and bulk Péclet numbers, respectively. The governing equations are coupled through a tangential stress balance at the interface, where a nonlinear Langmuir equation of state relates interfacial surface tension to surfactant concentration. The temporal evolution of the initial surfactant distribution is primarily influenced by several dimensionless parameters: the bulk and surface Péclet numbers, the Biot number (Bi), the solubility parameter (β), and the dimensionless surfactant depletion depth (α). Our findings indicate that the initial surfactant concentration is diminished due to diffusivity, and its decay toward a homogeneous state is significantly affected by solubility. The adsorption and desorption processes operate as an equilibrium mechanism that tends to homogenize the surface surfactant concentration.},
}

@article {pmid40521143,
year = {2025},
author = {Može, M and Jereb, S and Lovšin, R and Berce, J and Zupančič, M and Golobič, I},
title = {Dataset on droplet spreading and rebound behavior of water and viscous water-glycerol mixtures on superhydrophobic surfaces with laser-made channels.},
journal = {Data in brief},
volume = {61},
number = {},
pages = {111697},
pmid = {40521143},
issn = {2352-3409},
abstract = {Droplet impact, spreading and rebound was investigated experimentally on superhydrophobic laser-textured surfaces, yielding a dataset of 1498 datapoints. Data was collected on twelve types of surfaces with square grids of laser-made channels of various spacings (from 50 µm to 800 µm), with two groups of six surfaces possessing either deep or shallow laser-made channels. Droplet impact tests were performed with water and viscous water-glycerol mixtures with viscosity values up to 160 mPa·s and droplet impact behavior was images with a high-speed camera at 5000 fps. Maximum spreading factor, contact time, droplet rebound efficiency, and maximum lamella velocity were extracted from the videos using software image processing. Moreover, information on droplet diameter, velocity, density, surface tension, dynamic viscosity, Weber number, and Reynolds number are provided. A supplementary dataset includes the same quantitative information for droplet impacts on a smooth, hydrophobic surface, resembling the surface between the laser-made channels on other superhydrophobic surfaces (125 additional datapoints). Furthermore, scanning electron microscopy images of the surfaces are provided alongside the measurements of static and dynamic contact angles with water and water-glycerol mixtures. The data may be useful for fields like wettability studies, surface engineering, and anti-icing research. It can help validate theoretical and numerical models of droplet spreading, retracting, and rebounding from poorly wettable surfaces, optimize superhydrophobic surfaces for applications such as self-cleaning and drag reduction, and contribute to machine learning models predicting droplet behavior. The data is particularly relevant for designing anti-icing surfaces by minimizing contact time and maximizing the restitution coefficient. Additionally, it supports applications in 3D printing, coating technologies, and inkjet printing by providing data on viscous liquid impacts on poorly wettable surfaces.},
}

@article {pmid40518711,
year = {2025},
author = {Mikhil, S and Biswas, K and Bakshi, S},
title = {Measurement of Lamella Thickness Evolution during Droplet Spreading on a Dry Surface and Insights into Energy Distribution during the Process.},
journal = {Langmuir : the ACS journal of surfaces and colloids},
volume = {41},
number = {25},
pages = {16061-16072},
doi = {10.1021/acs.langmuir.5c01182},
pmid = {40518711},
issn = {1520-5827},
abstract = {The present study deals with the evolution of a liquid film formed by droplet impact onto a dry flat surface at high Weber and Reynolds numbers. A Chromatic Confocal Sensor is employed to measure the temporal evolution of the lamella thickness of the impacting droplet, and droplet spread factors are measured using shadow imaging. These measurements were then used to identify appropriate theoretical representations for different phases of the evolving droplet height/lamella thickness. The evolution of the lamella thickness is a critical input for estimating the energy dissipation in the boundary layer during lamella spread. Existing energy budgeting approaches consider a constant boundary layer thickness to estimate the boundary layer dissipation and predict the maximum spread of the droplet. The present study instead proposes the use of a transient boundary layer thickness along with a suitable velocity scale. Furthermore, the significance of considering early-stage energy dissipation in energy budgeting is demonstrated, and an approach for integrating both early-stage and wall boundary layer dissipations into an energy-based model is presented. A differential form of the energy balance equation is proposed for high Weber and Reynolds number impacts and is used to capture the time variation of the spreading diameter. The temporal evolution of the droplet spread factors obtained using this model is in good agreement with our measurements.},
}

@article {pmid40504656,
year = {2025},
author = {Juyal, M and Adhikari, S and Gautam, R and Bhaskar, T and Bhattacharya, S and Ghosh, D},
title = {β-Carotene Production by Oleaginous Yeasts in a Pilot Plant Fermenter: Yield Standardization and Process Scale-Up.},
journal = {Journal of agricultural and food chemistry},
volume = {73},
number = {25},
pages = {15767-15777},
doi = {10.1021/acs.jafc.5c02321},
pmid = {40504656},
issn = {1520-5118},
mesh = {*beta Carotene/biosynthesis/metabolism ; Fermentation ; *Rhodotorula/metabolism/growth & development ; *Bioreactors/microbiology ; Pilot Projects ; *Industrial Microbiology/methods/instrumentation/standards ; Biomass ; Culture Media/metabolism/chemistry ; },
abstract = {This study reports selective β-carotene pigment production by an oleaginous yeast, Rhodotorula mucilaginosa IIPL32 (MTCC 25056), in a 500 L fermenter working scale with a practically feasible approach for microbial pigment production scale-up from small (500 mL) to pilot scale (500 L) submerged fermenters using medium rheology and fermenter hydrodynamics. The pigment production was initially standardized by optimizing the carbon and nitrogen load of the fermentation medium. The pigment was purified using a solvent extraction process followed by thin-layer chromatography and analyzed by UV-visible spectrophotometry, high-pressure liquid chromatography, and Fourier-transform infrared spectroscopy, suggesting the dominant presence of β-carotene. Using 20 g/L glucose as a carbon feed, a 500 L fermenter yielded 3.3 kg yeast cell biomass and 5.1 g β-carotene. It was concluded that the process is scalable at an industrial level and could be integrated with any existing lipid biorefinery without any additional modification in Capex, thus substantially lowering the microbial lipid production cost.},
}

*beta Carotene/biosynthesis/metabolism
Fermentation
*Rhodotorula/metabolism/growth & development
*Bioreactors/microbiology
Pilot Projects
*Industrial Microbiology/methods/instrumentation/standards
Biomass
Culture Media/metabolism/chemistry

@article {pmid40504298,
year = {2025},
author = {Maeda, S and Otani, T and Yamada, S and Watanabe, Y and Wada, S},
title = {Subject-specific variability in cerebrospinal fluid flow characteristics through cerebral aqueducts in a healthy population: a magnetic resonance imaging and computational investigation.},
journal = {Medical & biological engineering & computing},
volume = {},
number = {},
pages = {},
pmid = {40504298},
issn = {1741-0444},
support = {23KJ1471//Japan Society for the Promotion of Science/ ; 23K11830//Japan Society for the Promotion of Science/ ; 24K02557//Japan Society for the Promotion of Science/ ; JPMXP1020230118//Ministry of Education, Culture, Sports, Science and Technology/ ; },
abstract = {Ventricular cerebrospinal fluid (CSF) flow has bi-directional flow profiles synchronized with cardiac pulsation. The increase in CSF stroke volume through the aqueduct (flow pathway between the third and fourth ventricle) is believed to be a biomarker of idiopathic normal pressure hydrocephalus (iNPH). However, several studies have reported that CSF stroke volume varies considerably even in healthy populations. To explore these variations from a fluid mechanics perspective, this study analyzed CSF flow characteristics in healthy individuals using magnetic resonance imaging (MRI)-based computational simulations. MRI data from 47 healthy subjects were acquired, and the maximum Reynolds number of the CSF flow through the aqueduct and the degree of CSF mixing were evaluated. Results showed that the Reynolds number of the CSF flow through the aqueduct was 28.6 ± 13.3, and the limited variation suggested fluid mechanical similarities of CSF flow characteristics in the healthy population. A positive correlation between CSF flow mixing and the Reynolds number was observed in both healthy populations and iNPH patients. These findings demonstrate that CSF flow through the aqueduct, especially in healthy populations, can be well characterized by examining fluid mechanical similarities.},
}

@article {pmid40493811,
year = {2025},
author = {Silva, A and Efrati, E},
title = {Path integral approach for predicting the diffusive statistics of geometric phases in chaotic Hamiltonian systems.},
journal = {Chaos (Woodbury, N.Y.)},
volume = {35},
number = {6},
pages = {},
doi = {10.1063/5.0271479},
pmid = {40493811},
issn = {1089-7682},
abstract = {From the integer quantum Hall effect to swimming at a low Reynolds number, geometric phases arise in the description of many different physical systems. In many of these systems, the temporal evolution prescribed by the geometric phase can be directly measured by an external observer. By definition, geometric phases rely on the history of the system's internal dynamics, and so their measurement is directly related to the temporal correlations in the system. They, thus, provide a sensitive tool for studying chaotic Hamiltonian systems. In this work, we present a toy model consisting of an autonomous, low-dimensional, chaotic Hamiltonian system designed to have a simple planar internal state space and a single geometric phase. The diffusive phase dynamics in the highly chaotic regime is, thus, governed by the loop statistics of planar random walks. We show that the naïve loop statistics result in ballistic behavior of the phase and recover the diffusive behavior by considering a bounded shape space or a quadratic confining potential.},
}

@article {pmid40468799,
year = {2025},
author = {Zhang, M and Shen, J and Liu, R and Cui, P and Wu, H and Liu, Z},
title = {A numerical study of circulating tumor cell behavior in constricted microvessels based on the immersed boundary-lattice Boltzmann method.},
journal = {Soft matter},
volume = {21},
number = {24},
pages = {4956-4967},
doi = {10.1039/d5sm00363f},
pmid = {40468799},
issn = {1744-6848},
mesh = {*Neoplastic Cells, Circulating/pathology ; *Microvessels/pathology ; Humans ; Cell Adhesion ; *Models, Biological ; Blood Platelets/cytology ; Erythrocytes/cytology ; },
abstract = {In this study, the lattice Boltzmann method (LBM) and the immersed boundary (IB) method are employed to quantitatively investigate the dynamics of circulating tumor cells (CTCs) at the cellular scale, and their interactions with red blood cells, platelets and microvascular wall are analyzed based on the obtained data. This reveals that CTC adhesion most likely occurs in the constricted vessels as the Reynolds number is around 0.01. An increase in hematocrit leads to enhanced adhesion, and cell stiffness influences the probability of adhesion. Furthermore, the activated platelets adhering to the CTCs exacerbate the metastatic spread, so the role of platelets in the deformation, adhesion and survival of tumor cells actively arrested by the endothelial cells is crucial. The findings in this work provide important quantitative insights into the underlying mechanisms of cancer metastasis.},
}

*Neoplastic Cells, Circulating/pathology
*Microvessels/pathology
Humans
Cell Adhesion
*Models, Biological
Blood Platelets/cytology
Erythrocytes/cytology

@article {pmid40460863,
year = {2025},
author = {Ford, MP and Santhanakrishnan, A},
title = {Metachronal rowing provides robust propulsive performance across four orders of magnitude variation in Reynolds number.},
journal = {Journal of the Royal Society, Interface},
volume = {22},
number = {227},
pages = {20240822},
pmid = {40460863},
issn = {1742-5662},
support = {//Division of Chemical, Bioengineering, Environmental, and Transport Systems/ ; },
mesh = {Animals ; *Swimming/physiology ; *Models, Biological ; Hydrodynamics ; Viscosity ; *Crustacea/physiology ; Biomechanical Phenomena ; },
abstract = {Metachronal rowing of multiple appendages is a swimming strategy used by numerous organisms across various taxa, with body sizes ranging of the orders of [Formula: see text] to [Formula: see text] m. This corresponds to a huge variation in fluid flow regimes, characterized by paddle-scale Reynolds numbers ([Formula: see text]) ranging from the orders of [Formula: see text] (viscosity dominated) to [Formula: see text] (inertially dominated). Though the rhythmic stroking of the paddles is conserved across species and developmental stages, the hydrodynamic scalability of metachronal rowing has not been examined across this broad [Formula: see text] range. Using a self-propelled metachronal paddling robot, we examine swimming performance changes across four orders of magnitude variation in [Formula: see text] most relevant to crustaceans ([Formula: see text] to [Formula: see text]). We found that wake Strouhal number ([Formula: see text]), which characterizes momentum transfer from paddles to the wake, was unchanged for [Formula: see text] ([Formula: see text]). This is within the reported range of Strouhal numbers of various flying and swimming animals. Peak dimensionless circulation of paddle tip vortices increased linearly with stroke kinematics but was mostly unaffected by fluid viscosity. These findings show that the swimming performance of metachronal rowing is conserved across widely varying flow regimes, with dimensionless swimming speed scaling linearly with [Formula: see text] across the entire tested range.},
}

Animals
*Swimming/physiology
*Models, Biological
Hydrodynamics
Viscosity
*Crustacea/physiology
Biomechanical Phenomena

@article {pmid40460369,
year = {2025},
author = {Sharma, KV and Naik, MT and Kanti, PK and Prasad, DMR and Paramasivam, P and Ayanie, AG},
title = {Flow and heat transfer of Poly Dispersed SiO2 Nanoparticles in Aqueous Glycerol in a Horizontal pipe: Application of ensemble and evolutionary machine learning for model-prediction.},
journal = {PloS one},
volume = {20},
number = {6},
pages = {e0323347},
pmid = {40460369},
issn = {1932-6203},
mesh = {*Silicon Dioxide/chemistry ; *Glycerol/chemistry ; *Nanoparticles/chemistry ; *Machine Learning ; Hot Temperature ; Water/chemistry ; Models, Theoretical ; },
abstract = {Stable nanofluid dispersion with SiO2 particles of 15, 50, and 100 nm is generated in a base liquid composed of water and glycerol in a 7:3 ratio and tested for physical characteristics in the temperature range of 20-100oC. The nanofluid showed excellent stability for over a month. Experiments are undertaken for the flow of nanofluid in a copper pipe and measured for their heat transfer coefficient and flow behavior. The convection heat transfer coefficient increases with the flow Reynolds number in the transition-turbulent flow regime. The experimental results further reveal that the friction factor enhancement with 0.5% concentration has increased by 6% as compared to the base liquid. It was employed for prognostic model development using XGBoost and multi-gene genetic programming (MGGP) to model and predict the complex and nonlinear data acquired during experiments. Both techniques provided robust predictions, as witnessed by the statistical evaluation. The R2 statistics of the XGBoost-based model was 0.9899 throughout the model test, while it was lowered to 0.9455 for the MGGP-based model. However, the change was insignificant. The mean squared value was 8.37 for XGBoost, while it increased in the MGGP model to 45.12. Similarly, the mean absolute error (MAE) value was higher (6.623) in the case of MGGP than in XGBoost at 2.733. The statistical evaluation, Taylor diagrams, and violin plots helped determine that XGBoost was superior to MGGP in the present work.},
}

*Silicon Dioxide/chemistry
*Glycerol/chemistry
*Nanoparticles/chemistry
*Machine Learning
Hot Temperature
Water/chemistry
Models, Theoretical

@article {pmid40455197,
year = {2025},
author = {Sudarsanan, S and Pavithran, I and Sujith, RI},
title = {On the nature of nonequilibrium phase transition in a complex system.},
journal = {Chaos (Woodbury, N.Y.)},
volume = {35},
number = {6},
pages = {},
doi = {10.1063/5.0265336},
pmid = {40455197},
issn = {1089-7682},
abstract = {The transition from a chaotic to a periodic oscillatory state can be smooth or abrupt in real-world complex systems. We study smooth and abrupt transitions in a turbulent reactive flow system. The turbulent reactive flow system consists of the flame, the acoustic field, and the hydrodynamic field interacting nonlinearly. Generally, as the Reynolds number is increased, a laminar flow becomes turbulent, and the range of time scales associated with the flow broadens. Yet, as the Reynolds number is increased in a turbulent reactive flow system, a single dominant time scale emerges in the acoustic pressure oscillations. By varying the Reynolds number at different rates, we observe smooth and abrupt transitions from chaos to order. For such smooth and abrupt transitions, we study the evolution of correlated (conformists and contrarians) and uncorrelated (disordered) dynamics between the acoustic pressure and the heat release rate oscillations in the spatiotemporal domain of the turbulent reactive flow system. We discover that the spatial extent of the disordered dynamics plays a critical role in deciding the abruptness of the transition. During the smooth transition, we observe a significant presence of disordered dynamics in the spatial domain. In contrast, abrupt transitions are accompanied by the abrupt disappearance of disordered dynamics from the spatial domain.},
}

@article {pmid40450040,
year = {2025},
author = {Tuo, D and Zeng, G and Zhang, Y and Liao, M},
title = {Effects of Reynolds number and scale ratio on VIV tests for railway blunt box girders.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {19146},
doi = {10.1038/s41598-025-02621-8},
pmid = {40450040},
issn = {2045-2322},
abstract = {Blunt steel box girder as a form of main girder used in large-span railway bridges, the vortex-induced vibrations (VIVs) phenomenon is significant. In order to investigate the effect of model scale on the test results of section model VIV tests of railway bridge blunt box girders, 1:90, 1:50 and 1:25 section model wind tunnel tests were carried out. The test results show that the VIV experimental results are greatly affected by the scale of the model, in which the amplitudes obtained from the 1:50 model test is the most significant, and the VIV characteristics of the two scale models of 1:50 and 1:25 coincide with each other roughly; However, the 1:90 small-scale model is not able to effectively respond to the VIV characteristics of the real bridge. The CFD numerical simulation results also confirm the phenomenon that the 1:90 small-scale model test cannot effectively respond to the real VIVs characteristics. Although VIVs, obtained in a small-scale model test, are not possible to determine the vibration response of the actual railway bridge, it can be used to compare the VIV performance of the cross-section and to assist in the study of aerodynamic optimization measures at the early design stage.},
}

@article {pmid40440770,
year = {2025},
author = {Rathore, S and Africa, PC and Ballarin, F and Pichi, F and Girfoglio, M and Rozza, G},
title = {Projection-based reduced order modelling for unsteady parametrized optimal control problems in 3D cardiovascular flows.},
journal = {Computer methods and programs in biomedicine},
volume = {269},
number = {},
pages = {108813},
doi = {10.1016/j.cmpb.2025.108813},
pmid = {40440770},
issn = {1872-7565},
mesh = {Humans ; *Models, Cardiovascular ; Hemodynamics ; Computer Simulation ; Blood Flow Velocity ; Finite Element Analysis ; Algorithms ; Imaging, Three-Dimensional ; Magnetic Resonance Imaging ; },
abstract = {BACKGROUND AND OBJECTIVE: Accurately defining outflow boundary conditions in patient-specific models poses significant challenges due to complex vascular morphologies, physiological conditions, and high computational demands. These challenges hinder the computation of realistic and reliable cardiovascular (CV) haemodynamics by incorporating clinical data such as 4D magnetic resonance imaging. The objective is to control the outflow boundary conditions to optimize CV haemodynamics and minimize the discrepancy between target and computed flow velocity profiles. This paper presents a projection-based reduced order modelling (ROM) framework for unsteady parametrized optimal control problems (OCP(μ)s) arising from CV applications.

METHODS: Numerical solutions of OCP(μ)s require substantial computational resources, highlighting the need for robust and efficient ROMs to perform real-time and many-query simulations. We investigate the performance of a projection-based reduction technique that relies on the offline-online paradigm, enabling significant computational cost savings. In this study, the fluid flow is governed by unsteady Navier-Stokes equations with physical parametric dependence, i.e. the Reynolds number. The Galerkin finite element method is used to compute the high-fidelity solutions in the offline phase. We implemented a nested-proper orthogonal decomposition (nested-POD) for fast simulation of OCP(μ)s that encompasses two stages: temporal compression for reducing dimensionality in time, followed by parametric-space compression on the precomputed POD modes.

RESULTS: We tested the efficacy of the proposed methodology on vascular models, namely an idealized bifurcation geometry and a patient-specific coronary artery bypass graft, incorporating stress control at the outflow boundary and observing consistent speed-up with respect to high-fidelity strategies. We observed the inter-dependency between the state, adjoint, and control solutions and presented detailed flow field characteristics, providing valuable insights into factors such as atherosclerosis risk.

CONCLUSION: The projection-based ROM framework provides an efficient and accurate approach for simulating parametrized CV flows. By enabling real-time, patient-specific modelling, this advancement supports personalized medical interventions and improves the predictions of disease progression in vascular regions.},
}

Humans
*Models, Cardiovascular
Hemodynamics
Computer Simulation
Blood Flow Velocity
Finite Element Analysis
Algorithms
Imaging, Three-Dimensional
Magnetic Resonance Imaging

@article {pmid40436033,
year = {2025},
author = {Fardi, A and Farooq, H and Akhtar, I and Hemmati, A and Saif Ullah Khalid, M},
title = {Characterizing the role of hind flippers in hydrodynamics of a harbor seal.},
journal = {Bioinspiration & biomimetics},
volume = {20},
number = {4},
pages = {},
doi = {10.1088/1748-3190/adde07},
pmid = {40436033},
issn = {1748-3190},
mesh = {Animals ; *Swimming/physiology ; Hydrodynamics ; Computer Simulation ; *Models, Biological ; *Phoca/physiology ; Friction ; *Hindlimb/physiology ; },
abstract = {In this paper, we investigate the hydrodynamic characteristics of harbor seal locomotion, focusing on the role of hind flippers in thrust generation and wake dynamics. Through three-dimensional numerical simulations using an immersed boundary method at Reynolds number of 3000, we analyze the impact of varying Strouhal number (St = 0.2-0.35) and propulsive wavelength (λ∗= 1.0-1.2) on swimming performance. Our findings reveal two distinct wake patterns: a single-row structure at lower Strouhal numbers (St⩽0.25) and a double-row configuration at higher St (St⩾0.3). Increasing wavelength generally enhances thrust production by reducing both pressure and friction of drag components. Additionally, we identify critical vortex interactions between the front and hind flippers, with destructive interference occurring at lower St and constructive patterns emerging at higher St. Circulation analysis confirms stronger vortex formation at higher St andλ∗, particularly during the left stroke phase. These results provide novel insights into the hydrodynamic mechanisms underlying seal locomotion and contribute to our understanding of efficient aquatic propulsion systems.},
}

Animals
*Swimming/physiology
Hydrodynamics
Computer Simulation
*Models, Biological
*Phoca/physiology
Friction
*Hindlimb/physiology

@article {pmid40430862,
year = {2025},
author = {Mattusch, AM and Schaldach, G and Bartsch, J and Thommes, M},
title = {Intrinsic Dissolution Modeling: Interdependence Between Dissolution Rate, Solubility, and Boundary Layer Thickness.},
journal = {Pharmaceutics},
volume = {17},
number = {5},
pages = {},
pmid = {40430862},
issn = {1999-4923},
abstract = {Background/Objectives: In the past, many drug release models have been presented which attempt to describe the interaction of drugs and excipients in a formulation. Nevertheless, modeling the intrinsic dissolution behavior is essential for understanding the fundamental dissolution mechanisms of drugs and for enhancing the quality of computational approaches in the long term. Methods: In this study, the intrinsic dissolution of various pharmaceutical model substances (benzocaine, carbamazepine, griseofulvin, ibuprofen, naproxen, phenytoin, theophylline monohydrate, and trimethoprim) was investigated in dissolution experiments, taking into account the flow conditions in a dissolution channel apparatus. A practicable and generally valid representation was identified to describe the diffusion properties of the drugs in terms of the boundary layer thickness without considering the particle size distribution, physical state, or viscoelastic properties. This representation was supported by numerical simulations using a high-resolution mesh. The influence of the topography on the modeling was also examined. Results: Besides the prediction of the influence of a surface reaction limitation or the solubility of a diffusion controlled drug, the boundary layer thickness at the tablet surface is modellable in terms of a freely selectable length and as a function of the diffusion coefficient, drug solubility, and the flow velocity of the dissolution medium. Conclusions: Using different methods and a large dataset, this study presents a modeling approach that can contribute to a deeper understanding of intrinsic dissolution behavior.},
}

@article {pmid40428718,
year = {2025},
author = {Juraeva, M and Kang, DJ},
title = {Design and Analysis of a Passive Micromixer Based on Multiple Passages.},
journal = {Micromachines},
volume = {16},
number = {5},
pages = {},
pmid = {40428718},
issn = {2072-666X},
abstract = {We propose a novel passive micromixer based on multiple passages and analyze its mixing performance comprehensively. The multiple passages are constructed with straight channels, making them easier to manufacture, compared to conventional SAR micromixers and other micromixers based on curved channels. Its mixing performance has been demonstrated to be superior to that of the previous micromixers across a broad range of Reynolds numbers. Five distinct designs incorporating converging passages were explored to study the significance of the number of passages on the mixing performance. Across a broad range of Reynolds number ranges (0.1 to 80), the two-passage design significantly improved mixing performance, with a degree of mixing (DOM) consistently exceeding 0.84. Particularly, the mixing enhancement is prominent within the low and intermediate range of Reynolds numbers (Re≤20). This enhancement in the regime of molecular diffusion dominance stems from the elongated interface between the two fluids. The mixing enhancement in the transition regime is due to a secondary flow being generated on the cross-section normal to the main stream direction. The intensity of this secondary flow is significantly influenced by the number of multiple passages. The optimal number for the present micromixer design is two. The DOM remains almost constant for the submergence of multiple passages in the range of 40 to 70 (μm).},
}

@article {pmid40428712,
year = {2025},
author = {Moscato, S and Cutuli, E and Camarda, M and Bucolo, M},
title = {Experimental and Numerical Study of Slug-Flow Velocity Inside Microchannels Through In Situ Optical Monitoring.},
journal = {Micromachines},
volume = {16},
number = {5},
pages = {},
pmid = {40428712},
issn = {2072-666X},
support = {CUP: E63C220009000022//MUR-PNRR project SAMOTHRACE/ ; },
abstract = {Miniaturization and reliable, real-time, non-invasive monitoring are essential for investigating microfluidic processes in Lab-on-a-Chip (LoC) systems. Progress in this field is driven by three complementary approaches: analytical modeling, computational fluid dynamics (CFD) simulations, and experimental validation techniques. In this study, we present an on-chip experimental method for estimating the slug-flow velocity in microchannels through in situ optical monitoring. Slug flow involving two immiscible fluids was investigated under both liquid-liquid and gas-liquid conditions via an extensive experimental campaign. The measured velocities were used to determine the slug length and key dimensionless parameters, including the Reynolds number and Capillary number. A comparison with analytical models and CFD simulations revealed significant discrepancies, particularly in gas-liquid flows. These differences are mainly attributed to factors such as gas compressibility, pressure fluctuations, the presence of a liquid film, and leakage flows, all of which substantially affect flow dynamics. Notably, the percentage error in liquid-liquid flows was lower than that in gas-liquid flows, largely due to the incompressibility assumption inherent in the model. The high-frequency monitoring capability of the proposed method enables in situ mapping of evolving multiphase structures, offering valuable insights into slug-flow dynamics and transient phenomena that are often difficult to capture using conventional measurement techniques.},
}

@article {pmid40428670,
year = {2025},
author = {Li, Y and Yonemoto, Y and Yamahata, Y and Kawahara, A},
title = {Rheological Property Changes in Polyacrylamide Aqueous Solution Flowed Through Microchannel Under Low Reynolds Number and High Shear Rate Conditions.},
journal = {Micromachines},
volume = {16},
number = {5},
pages = {},
pmid = {40428670},
issn = {2072-666X},
support = {22K03907 and 21K03860//JSPS KAKENHI/ ; },
abstract = {As an important structure of microfluidic devices, microchannels have the advantages of precise flow control and high reaction efficiency. This study investigates experimentally changing the rheological properties of a polyacrylamide (PAM) aqueous solution after flowing through a square microchannel with a hydraulic diameter of 0.5 mm under low Reynolds number and high shear rate conditions. To know the effect of the channel length on the change in viscosity and relaxation time, the length is changed to 100 mm and 200 mm. From the experiment, it is found that both the viscosity and relaxation time of the solution decrease with increasing the shear rate and the microchannel length. Based on the present experimental data, an empirical model is proposed to predict the change ratio of the relaxation time before and after passing through the microchannel, and the calculation with the model has an agreement with the experiment with root-mean-square absolute error of 0.007.},
}

@article {pmid40428660,
year = {2025},
author = {Lu, X and Wang, L and Wang, L and Hu, Y},
title = {Heat Transfer Enhancement of Diamond Rib Mounted in Periodic Merging Chambers of Micro Channel Heat Sink.},
journal = {Micromachines},
volume = {16},
number = {5},
pages = {},
pmid = {40428660},
issn = {2072-666X},
support = {52476076//National Natural Science Foundation of China/ ; 21ZD4GA027//Major Special Projects of Gansu Province, China/ ; 25JRRA963,23JRRA1704//Science and Technology Program Basic research program natural science Foundation of Gansu Province China/ ; },
abstract = {The heat transfer enhancement of diamond-shaped ribs mounted in the periodic merging chambers of microchannel (MC) heat sinks is investigated using a numerical method for Reynolds number in the region of 300-700. Compared to triangular, rectangular, and cylindrical ribs, diamond-shaped ribs achieve 3.59%, 13.24%, and 6.34% higher enhancement effects, respectively, under the same mass flow rate. Further analysis of geometric parameters (length, width, and height) and rib positioning reveals that a rib height of h/Hch = 0.8 provides optimal heat dissipation performance. For Re < 500, the optimal configuration is a rib length of l/Lmerg = 0.55 and a width of b/Wch = 0.8, while for 500 < Re < 700, it shifts to l/Lmerg = 0.36 and b/Wch = 1.6. For s/Lmerg, the smaller it is, the shorter the main flow separation time, thereby improving heat transfer efficiency.},
}

@article {pmid40423248,
year = {2025},
author = {Wirth, M and Hagedorn, J and Weigand, B and Kabelac, S},
title = {Design of a test rig for the investigation of falling film flows with counter-current gas flows.},
journal = {The Review of scientific instruments},
volume = {96},
number = {5},
pages = {},
doi = {10.1063/5.0263158},
pmid = {40423248},
issn = {1089-7623},
abstract = {Geothermal phase change probes employ falling film evaporation to efficiently harness geothermal heat for space heating applications. Despite successful applications in research, commercial use remains limited due to the lack of validated models capable of accurately representing the complex flow phenomena within these probes. To address this issue, a test rig was developed, replicating the flow phenomena within these probes and facilitating the validation of future models. This paper presents the results of the first measurement campaign conducted with water and humid air as working fluids. For the gas phase, velocity profiles were measured with a hot-wire anemometer, and for the liquid phase, high temporal resolution film thickness measurements were conducted with a confocal chromatic imaging sensor. The results of both measurement systems were qualitatively consistent with existing literature. The time-averaged film thickness h̄film in the flow direction, without gas flow, revealed an increase of h̄film along the flow direction for Reliq = 500. In contrast, for Reliq ≥ 980, an opposing trend was observed. In addition, the influence of the gas flow on h̄film was investigated in the flow direction. The results show no noticeable influence below a threshold gas Reynolds number near the liquid film inlet (x = 0.1 m), while an increase appeared beyond this Reliq-dependent value. Observations further downstream (x = 0.6 m) indicated an h̄film increase toward the threshold and a decrease beyond it. The latter observation aligns with findings in the literature, suggesting the onset of flooding. This observation was further strengthened by a film flow transition captured through high-speed camera imaging, indicating the test rig's capability of investigating flooding conditions.},
}

@article {pmid40422158,
year = {2025},
author = {Li, K and Xu, N and Zhong, L and Mou, X},
title = {Corrugation at the Trailing Edge Enhances the Aerodynamic Performance of a Three-Dimensional Wing During Gliding Flight.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {10},
number = {5},
pages = {},
pmid = {40422158},
issn = {2313-7673},
support = {11802262//National Natural Science Foundation of China/ ; 11502228//National Natural Science Foundation of China/ ; },
abstract = {Dragonflies exhibit remarkable flight capabilities, and their wings feature corrugated structures that are distinct from conventional airfoils. This study investigates the aerodynamic effects of three corrugation parameters on gliding performance at a Reynolds number of 1350 and angles of attack ranging from 0° to 20°: (1) chordwise corrugation position, (2) linear variation in corrugation amplitude toward the trailing edge, and (3) the number of trailing-edge corrugations. The results show that when corrugation structures are positioned closer to the trailing edge, they generate localized vortices in the mid-forward region of the upper surface, thereby enhancing aerodynamic performance. Further studies show that a linear increase in corrugation amplitude toward the trailing edge significantly delays the shedding of the leading-edge vortex (LEV), produces a more coherent LEV, and reduces the number of vortices within the corrugation grooves on the lower surface. Consequently, the lift coefficient is maximized with an enhancement of 28.99%. Additionally, reducing the number of trailing-edge corrugations makes the localized vortices on the upper surface approach the trailing edge and merge into larger, more continuous LEVs. The vortices on the lower surface grooves also decrease in number, and the lift coefficient is maximally increased by 20.09%.},
}

@article {pmid40422087,
year = {2025},
author = {Shanmugam, AR and Sohn, CH and Park, KS},
title = {Numerical Investigation on the Aerodynamic Benefits of Corrugated Wing in Dragonfly-like Hovering Flapping Wing.},
journal = {Biomimetics (Basel, Switzerland)},
volume = {10},
number = {5},
pages = {},
pmid = {40422087},
issn = {2313-7673},
support = {G00004258//United Arab Emirates University/ ; G00004882//United Arab Emirates University/ ; },
abstract = {The effect of corrugated wings on the aerodynamic characteristics of a dragonfly-like hovering flapping wing is investigated using two-dimensional numerical simulations. Two types of pitch motion profiles, namely 'sinusoidal' and 'trapezoidal', are employed. The results obtained from the corrugated wings at Reynolds number Re = 2150 are then compared with the flat plate geometries to analyze the aerodynamic benefits of wing corrugation. The aerodynamic characteristics of corrugated wings are investigated quantitatively using cycle-averaged vertical force coefficient. For the qualitative investigation, time histories of vertical force coefficient, vorticity, and surface pressure distribution are used. The results reveal that the corrugated wings perform better than the flat plates in all three flapping configurations for both sinusoidal and trapezoidal pitch profiles. For a tandem wing with a sinusoidal pitch profile, the corrugated wings yield a vertical force generation nearly 14%, 22%, and 12%, higher than the flat plate geometries for ψ = 0°, 90°, and 180°, respectively. The corrugated wing sheds a relatively stronger detached counter clockwise vortex (CCWV) on the lower surface as compared to the flat plate, and hence, the vertical force is much higher for the corrugated wing. For a tandem wing with a trapezoidal pitch profile, the corrugated wings yield a vertical force generation nearly 27%, 22%, and 57%, higher than the flat plate geometries for ψ = 0°, 90°, and 180°, respectively. In corrugated wing geometry, the delayed stall mechanism is slightly postponed due to the corrugation shape's ability to trap the vortex structures, leading to a positive effect on vertical force production.},
}

@article {pmid40415832,
year = {2025},
author = {Zou, S and Xiao, J and Chen, XD},
title = {A Comprehensive Comparison of Different Reynolds-Averaged Navier-Stokes Turbulence Models in Modeling Turbulent Plane Jets.},
journal = {ACS omega},
volume = {10},
number = {19},
pages = {19873-19886},
pmid = {40415832},
issn = {2470-1343},
abstract = {Turbulent plane jets are of great interest in a broad range of engineering applications such as combustion, mixing, and ventilation. Accurate prediction of the velocity field of jets is essential for accurate calculation of the mass and energy transfer in it. However, to date, no modeling works has comprehensively evaluated the computational accuracy and advantages of various Reynolds-averaged Navier-Stokes (RANS) turbulence models for calculating plane jets. Here, the plane jet of air was investigated under various Reynolds numbers using a suite of RANS models, including standard k - ε (SKE), realizable k - ε (RKE), renormalization group k - ε (RNGKE), standard k - ω (SKO), and shear-stress transport k - ω (SSTKO). The velocity fields were comprehensively compared to the experimental results. It was found that the SKO model exhibits a significant mesh dependency and poor convergence. No model can accurately predict the effect of the Reynolds number on velocity fields with an accuracy of R [2] ≥ 0.97. Moreover, (1) the SKE model has the best prediction under low or moderate Reynolds numbers (Re ≤ 10000); (2) the RKE model is more applicable under high Reynolds numbers (Re ≥ 10000); (3) the RNGKE model has the worst prediction; (4) the SSTKO model is more applicable under moderate Reynolds numbers (3000 ≤ Re ≤ 10000). It is hoped that these results can guide the selection of RANS models and stimulate greater efforts in creating an appropriate turbulence model that can accurately model such a "simple" case of flow.},
}

@article {pmid40415070,
year = {2025},
author = {Javed, SF and Khan, ME and Yahya, Z and Idrisi, MJ and Tenna, W},
title = {Performance analysis of three-dimensional passive micromixers using k-means priority clustering with AHP-based sustainable design optimization.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {18140},
pmid = {40415070},
issn = {2045-2322},
abstract = {This novel study presents an in-depth mathematical analysis, investigation, and comparative peculiar assessment of mixing behaviors across different microchannel configurations: the Simple T-shape, Spiral T-shape, and Three-Dimensional Serpentine Passive Micromixer (TDSPM). Considering the pivotal role of micromixing in various applications, the research thoroughly employs the Navier-Stokes equations to analyze flow dynamics and measure the mixing performance of water and water-dye mixtures. The TDSPM, with its distinctive rectangular inlet duct and U-shaped repeating structures, optimizes fluid interaction by constricting flow pathways. The study highlights the superior performance of the TDSPM and thoroughly evaluates the mixing indices for all three micromixer types at Reynolds numbers ranging from 5 to 250. From the priority analysis, Reynolds number (38.49%) and velocity (38.69%) are the most influential factors in micromixer performance, followed by mixing path length (15.35%) and channel width (6.87%). Test 18 (Re = 200, Mixing Path = 25 mm, Velocity = 4.2 m/s, Channel Width = 5 mm) achieves 98% mixing efficiency with a 500 Pa pressure drop, optimizing performance with lower energy costs. Finally, this design leads to remarkable improvements in mixing efficiency over a broad spectrum of Reynolds numbers.},
}

@article {pmid40414908,
year = {2025},
author = {Ma, H and Sun, X and Li, Y},
title = {Design of structural parameters and study on the energy dissipation characteristics of vertical jet-type energy dissipators.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {18204},
pmid = {40414908},
issn = {2045-2322},
support = {202303021211141//Natural Science Foundation for Young Scientists of Shanxi Province/ ; 202303021211141//Natural Science Foundation for Young Scientists of Shanxi Province/ ; 202303021211141//Natural Science Foundation for Young Scientists of Shanxi Province/ ; 51179116//the National Natural Science Foundation of China/ ; 51179116//the National Natural Science Foundation of China/ ; 51179116//the National Natural Science Foundation of China/ ; },
abstract = {In order to isolate energy dissipators from hydraulic engineering projects and address the issues of vibration damage caused by the discharge structures. This study develops a novel vertical jet-type energy dissipator by placing fragmentation needles at the vertical jet pipe nozzle, which mainly uses the fragmentation needles to fragment the high-energy jet into multiple smaller jets. Along with the mixing of air into the water flow, the mechanical energy of the flow is converted into internal energy and dissipated in the air. The structural parameters of the vertical jet-type energy dissipator include the size, shape, and number of fragmentation needles. The study employs numerical simulations primarily, with physical model experiments for validation, to investigate the nappe characteristics, energy dissipation rate, and energy dissipation mechanisms of the vertical jet energy dissipator under various structural parameters. The results show that within the scope of this study, the energy dissipation rate of the vertical jet increases with the Reynolds number, the number of fragmentation needles, and the size of the fragmentation needles. Compared to the case without fragmentation needles, the energy dissipation rate increases by 1.04-4.89 times. Under the same Reynolds number, the total height of the jet and the height of the potential core decrease as the number and size of the fragmentation needles increase. The height and diameter of the nappe crown increase, and the diameter and thickness of the vortex ring decrease as the number and size of the fragmentation needles increase. The jet under the influence of rectangular fragmentation needles is more dispersed compared to the jet under the influence of cylindrical fragmentation needles. The total height and potential core height of the jet are smaller with rectangular fragmentation needles, while the height and diameter of the nappe crown are larger. The air concentration in the nappe under rectangular fragmentation needles is higher than that under cylindrical fragmentation needles, and the energy dissipation rate of the vertical jet is also higher under rectangular fragmentation needles than under cylindrical fragmentation needles. The vertical jet-type energy dissipator proposed in this study addresses key engineering challenges, such as terrain constraints and the need for flexible design solutions. Its ability to efficiently dissipate energy while maintaining adaptability makes it a valuable tool for hydraulic engineers designing energy dissipation systems. The conclusions of this study provide a reference for the application of vertical jet-type energy dissipators.},
}

@article {pmid40411012,
year = {2025},
author = {Jiang, H and Pfister, JL and Huang, DZ and Cao, S},
title = {Koopman reduced-order modeling and analysis of flag flapping in the wake of a cylinder.},
journal = {Physical review. E},
volume = {111},
number = {4-2},
pages = {045101},
doi = {10.1103/PhysRevE.111.045101},
pmid = {40411012},
issn = {2470-0053},
abstract = {We develop a Koopman reduced-order model (ROM) to analyze the instability mechanism and predict the hydrodynamic behavior for the flag flapping in the wake of a cylinder. The Koopman ROM is constructed using a kernel dynamic mode decomposition method and enhanced through a residual dynamical mode decomposition algorithm, which improves accuracy by identifying and eliminating spurious modes. Our analysis reveals a flow transition from the "2S" mode in the periodic phase to the "2P" mode in the quasiperiodic phase, with the main Koopman mode M_{1}
providing insights into the instability mechanism. In the case of chaotic flapping at a Reynolds number of Re=1200, the Koopman ROM demonstrates high accuracy in predicting the chaotic fluid-structure interaction flow when comparing the fractal dimension d_{c}
and the maximum Lyapunov exponent λ_{max}
of the true and reconstructed flow. Additionally, we observe similar flag flapping and vortex shedding characteristics in the near-structure region throughout the investigated Reynolds number range Re∈[500,1200], leading to similar vorticity patterns for M_{1}.
The flag flapping has a local minimum displacement at position x_{0}�
��3.0 in the flag's displacement envelope. Notably, this position closely matches the critical position x_{c}
obtained from global linear instability analysis at low Reynolds numbers. This conclusion aligns with the performance of the Koopman ROM using sparse measurement probes attached to the flag. The position of the probes influences the accuracy of the ROM, where higher accuracy corresponds to a larger displacement of the eigenfunction.},
}

@article {pmid40406451,
year = {2025},
author = {Suárez, P and Alcántara-Ávila, F and Miró, A and Rabault, J and Font, B and Lehmkuhl, O and Vinuesa, R},
title = {Active Flow Control for Drag Reduction Through Multi-agent Reinforcement Learning on a Turbulent Cylinder at R e D = 3900.},
journal = {Flow, turbulence and combustion},
volume = {115},
number = {1},
pages = {3-27},
pmid = {40406451},
issn = {1573-1987},
abstract = {This study presents novel drag reduction active-flow-control (AFC) strategies for a three-dimensional cylinder immersed in a flow at a Reynolds number based on freestream velocity and cylinder diameter of R e D = 3900 . The cylinder in this subcritical flow regime has been extensively studied in the literature and is considered a classic case of turbulent flow arising from a bluff body. The strategies presented are explored through the use of deep reinforcement learning. The cylinder is equipped with 10 independent zero-net-mass-flux jet pairs, distributed on the top and bottom surfaces, which define the AFC setup. The method is based on the coupling between a computational-fluid-dynamics solver and a multi-agent reinforcement-learning (MARL) framework using the proximal-policy-optimization algorithm. This work introduces a multi-stage training approach to expand the exploration space and enhance drag reduction stabilization. By accelerating training through the exploitation of local invariants with MARL, a drag reduction of approximately 9 % is achieved. The cooperative closed-loop strategy developed by the agents is sophisticated, as it utilizes a wide bandwidth of mass-flow-rate frequencies, which classical control methods are unable to match. Notably, the mass cost efficiency is demonstrated to be two orders of magnitude lower than that of classical control methods reported in the literature. These developments represent a significant advancement in active flow control in turbulent regimes, critical for industrial applications.},
}

@article {pmid40374935,
year = {2025},
author = {Xu, L and Miao, Y and Wu, X and Li, P and Qin, H},
title = {Experimental investigation on loads of nets with different types under current.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {16891},
pmid = {40374935},
issn = {2045-2322},
support = {BK20220221//Jiangsu Province Science Foundation for Youths/ ; },
abstract = {The drag of the net is the main component of the total hydrodynamic loads on the cage. It is crucial to the operational safety and structural integrity of the net cage. Despite this, there is a paucity of research examining the impact of various parameters, including materials, mesh types, solidity ratios, and angles of attack, on the hydrodynamic loads of nets. In this paper, a series of flume tests are used to investigate the drag on the nets and the relationships between the drag coefficient and the net material, net solidity ratio, mesh shape, current velocity, and current direction. The drag of six nets with different types under varying current velocities and current directions are calculated, and the curves between the drag coefficient and the current velocity or Reynolds number are further obtained. The test results show that the drag and drag coefficients of the net are not only related to the current velocity and the windward area but also to the mesh shape, net solidity ratio, material properties, etc. On this basis, the drag coefficients of these nets obtained from the prediction models and the tests are compared and analyzed, and the applicable conditions of different prediction models are further clarified. This paper can provide data support for the drag calculation of the cage.},
}