@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},
doi = {10.1371/journal.pone.0327916},
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},
doi = {10.1098/rsta.2024.0366},
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},
doi = {10.1126/sciadv.adu8634},
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},
doi = {10.1038/s41378-024-00862-7},
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 = {},
number = {},
pages = {},
doi = {10.1088/1748-3190/adebcf},
pmid = {40609600},
issn = {1748-3190},
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 hindwing 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-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. The comparative study reveals that the tandem wing configuration maintains efficiency comparable to that of a single wing while allowing us to utilize its advantages for MAV applications.},
}

@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},
doi = {10.1073/pnas.2426598122},
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 = {},
number = {},
pages = {},
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 = {},
number = {},
pages = {},
doi = {10.1021/acs.jafc.5c02321},
pmid = {40504656},
issn = {1520-5118},
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.},
}

@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 = {},
number = {},
pages = {},
doi = {10.1039/d5sm00363f},
pmid = {40468799},
issn = {1744-6848},
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.},
}

@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},
doi = {10.1098/rsif.2024.0822},
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},
doi = {10.1371/journal.pone.0323347},
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},
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},
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.},
}

@article {pmid40436033,
year = {2025},
author = {Fardi, A and Farooq, H and Akhtar, I and Hemmati, A and Khalid, MSU},
title = {Characterizing the Role of Hind Flippers in Hydrodynamics of A Harbor Seal.},
journal = {Bioinspiration & biomimetics},
volume = {},
number = {},
pages = {},
doi = {10.1088/1748-3190/adde07},
pmid = {40436033},
issn = {1748-3190},
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 and λ∗, 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.},
}

@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 = {},
doi = {10.3390/pharmaceutics17050570},
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 = {},
doi = {10.3390/mi16050592},
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 = {},
doi = {10.3390/mi16050586},
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 = {},
doi = {10.3390/mi16050545},
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 = {},
doi = {10.3390/mi16050533},
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 = {},
doi = {10.3390/biomimetics10050329},
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 = {},
doi = {10.3390/biomimetics10050256},
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.},
}

@article {pmid40372907,
year = {2025},
author = {Xiao, X and Lin, D and Wu, Y and Bai, K and Liu, X},
title = {Simulating Two-phase Fluid-rigid Interactions with an Overset-Grid Kinetic Solver.},
journal = {IEEE transactions on visualization and computer graphics},
volume = {PP},
number = {},
pages = {},
doi = {10.1109/TVCG.2025.3570570},
pmid = {40372907},
issn = {1941-0506},
abstract = {Simulating the coupled dynamics between rigid bodies and two-phase fluids, especially those with a large density ratio and a high Reynolds number, is computationally demanding but visually compelling with a broad range of applications. Traditional approaches that directly solve the Navier-Stokes equations often struggle to reproduce these flow phenomena due to stronger numerical diffusion, resulting in lower accuracy. While recent advancements in kinetic lattice Boltzmann methods for two-phase flows have notably enhanced efficiency and accuracy, challenges remain in correctly managing fluid-rigid boundaries, resulting in physically inconsistent results. In this paper, we propose a novel kinetic framework for fluid-rigid interaction involving two fluid phases. Our approach leverages the idea of an overset grid, and proposes a novel formulation in the two-phase flow context with multiple improvements to handle complex scenarios and support moving multi-resolution domains with boundary layer control. These new contributions successfully resolve many issues inherent in previous methods and enable physically more consistent simulations of two-phase flow phenomena. We have conducted both quantitative and qualitative evaluations, compared our method to previous techniques, and validated its physical consistency through real-world experiments. Additionally, we demonstrate the versatility of our method across various scenarios.},
}

@article {pmid40372072,
year = {2025},
author = {Kumar, S and Bhumkar, YG},
title = {Beat of sound generated from NACA0012 airfoil on application of suction-blowing excitation.},
journal = {The Journal of the Acoustical Society of America},
volume = {157},
number = {5},
pages = {3730-3741},
doi = {10.1121/10.0036698},
pmid = {40372072},
issn = {1520-8524},
abstract = {The present numerical study explores the effect of periodic suction-blowing excitation (SBE) on sound generation in the flow over a NACA0012 airfoil, with a focus on inducing beats in the resulting sound signals. Simulations are conducted at a Reynolds number (Re) of 5000 and an angle of attack of 5° using direct numerical simulation (DNS) approach where compressible Navier-Stokes equations are solved to compute both flow and sound fields directly. At low Re, vortex-shedding generates tonal noise at the Strouhal frequency (St). The introduction of periodic SBE adds sound sources at the excitation frequency (ff), with the resultant sound field arising from the interaction between vortex-shedding and excitation-induced sound sources. This study investigates the effects of excitation forcing frequency (ff) and amplitude (Ae), identifying conditions that lead to beat formation. Beats are observed when ff is close to St and the sound intensities of both sources are comparable. Distinct wave propagation patterns emerge during beat formation, significantly differing from non-beat scenarios. A key contribution of this work is to offer a guideline on the relationship between excitation amplitude and the formation of sound beats, either in the axial direction of flow or normal to it.},
}

@article {pmid40343671,
year = {2025},
author = {Li, Z and He, L and Pan, T and Yin, Y and Li, S and Yuan, W and Meng, B},
title = {Influence of the stability of boundary vortex on drag reduction induced by transverse V-grooves.},
journal = {The European physical journal. E, Soft matter},
volume = {48},
number = {4-5},
pages = {24},
pmid = {40343671},
issn = {1292-895X},
support = {52176032//National Natural Science Foundation of China/ ; 52322603//National Natural Science Foundation of China/ ; 52006002//National Natural Science Foundation of China/ ; },
abstract = {Previous studies revealed the skin-friction drag reduction properties induced by transverse grooves. However, the effects of unsteady characteristics of vortices within the grooves on the drag reduction properties have not been investigated. A hypothesis that the unsteady motion of vortices may reduce the friction drag-reduction rate induced by transverse V-grooves is proposed in this paper. To verify this hypothesis, we use the LES (large eddy simulation) method to investigate the flow field in the range of Reynolds number 0.5E5 to 7.5E5 over the different profiles of symmetric V-grooves, whose depths are 0.2 mm and AR's are 0.5, 1, 2, 5, and 8. The results show that the AR (aspect ratio of a transverse groove) affects the stability of boundary vortices, thus driving the variation of total viscous drag and pressure drag. With the increase of AR, the boundary vortices tend to be stable at first and then gradually become unstable. When AR is 2, the boundary vortices are stable within the grooves, corresponding to optimal drag reduction. In this case, the slip velocities induced by boundary vortices are the largest, and the Reynolds shear stress is the least, suggesting that the grooves have the strongest abilities to reduce the total viscous drag. When the stability of the boundary vortices is broken, a larger area containing high pressure and low pressure is formed in the groove, and the difference also becomes greater between the high pressure and low pressure. The results provide improved understandings of the drag reduction mechanism of transverse grooves.},
}

@article {pmid40341596,
year = {2025},
author = {Kanti, PK and Wanatasanappan, VV and Said, NM and Saini, S and Mishra, V and Paramasivam, P and Yusuf, M},
title = {Thermal performance, entropy generation, and machine learning insights of Al2O3-TiO2 hybrid nanofluids in turbulent flow.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {16035},
pmid = {40341596},
issn = {2045-2322},
abstract = {This study investigates the heat transfer performance of water-based Al2O3-TiO2 (50:50) hybrid nanofluids under turbulent flow conditions. Al2O3 and TiO2 nanoparticles (13 and 21 nm, respectively) were dispersed in water to prepare the nanofluids in the concentrations range of 0 to 1 vol%. Thermal conductivity and viscosity are measured in the temperature range of 30 to 60[o]C for the prepared nanofluids. Experimental and numerical analyses explored the effect of concentration and Reynolds number on Nusselt number, entropy generation, and friction factor. The results demonstrate that maximum viscosity enhancement of 15.77 and 14.76% is observed for 1 vol% of hybrid nanofluid and Al2O3 nanofluid compared to base fluid at 30 [o]C, respectively. The maximum Nusselt number enchantment is 70.4% for 1 vol% of hybrid nanofluid compared to the water. Similarly, hybrid nanofluids achieved a remarkable reduction in total entropy generation of 46% in contrast to the base fluid. New correlations are proposed to predict both the Nusselt number and friction factor for hybrid nanofluids. Furthermore, employing machine learning techniques, highly accurate models are developed. These findings highlight the promising role of hybrid nanofluids in achieving efficient thermal management in various applications.},
}

@article {pmid40331166,
year = {2018},
author = {Baek, S and Bradley, PE and Radebaugh, R},
title = {Heat transfer coefficient measurement of LN2 and GN2 in a microchannel at low Reynolds flow.},
journal = {International journal of heat and mass transfer},
volume = {127},
number = {},
pages = {},
doi = {10.1016/j.ijheatmasstransfer.2018.07.145},
pmid = {40331166},
issn = {0017-9310},
abstract = {The heat transfer coefficients of single-phase fluids in the laminar flow regime have been studied for decades. However, inconsistent results are found in the literature. The common finding is that the Nusselt number is dependent on the Reynolds number in the laminar flow regime, which is contrary to laminar flow heat transfer theory. Recently, researchers indicated that axial conduction in the wall of the microchannel can affect the measurement. However, there have not been thorough studies that demonstrate consistency or lack thereof between experiment and theory. This study provides an experimental investigation on heat transfer performance of gaseous and liquid nitrogen flow through microchannels with hydraulic diameters of 110 μm and 180 μm. A model has been developed to investigate heat transfer in a microchannel from which analysis shows that the temperature profile of the fluid and wall change non-linearly along the length of the microchannel when the flow rate is low (e.g., R e < 1000). The nonlinear temperature profile conflicts with the assumption of a linear temperature profile commensurate with the traditional Nusselt number estimation method, which leads to dependency on the Reynolds number. Comparison between the experiment and numerical model of the present work validates the conclusion that the heat transfer coefficient is uniform within the laminar flow regime (R e < 2000) for microchannels.},
}

@article {pmid40322754,
year = {2025},
author = {Rosi, G and Barnes, M and Kaiser, F and Rival, D},
title = {Exploring separation and reattachment in shear-thinning suspensions through pipe-wall ultrasound measurements.},
journal = {Experiments in fluids},
volume = {66},
number = {5},
pages = {99},
pmid = {40322754},
issn = {0723-4864},
abstract = {To better understand how turbulent flow structures develop within shear-thinning suspensions (STSs), we investigate the behavior of a shear layer forming within an STS downstream of a sudden expansion with an expansion ratio of 0.5. Specifically, the shear-layer reattachment behavior downstream of an axisymmetric expansion is characterized through ultrasound imaging velocimetry (UIV) and through pressure measurements, and the observed behavior is used to surmise how the shear layer is modified within the STS. Four fluids are investigated, which include pure water, as well as three 1750 ppm xanthan-gum-in-water solutions mixed with non-reactive mineral microspheres at volume fractions of 0%, 15%, and 30%. Wall-pressure measurements were collected through pressure taps located at 0h to 25.8h downstream of the expansion with subsequent UIV measurements collected from 1h to 9h downstream of the expansion, where h is the step height and equals the difference between the pipe and throat radii. For single-phase cases, pressure-recovery profiles and UIV flow fields indicate a predictably large reattachment length at low Reynolds numbers, which shortens as the Reynolds number increases from O (10 2) to O (10 4) and finally stabilizes at roughly 8h. In contrast, the STSs exhibit pressure-recovery and pipe-wall velocity profiles indicating a reattachment length that is consistently short (8h) and independent of Reynolds number. The results indicate that the suspended phase within the STSs causes the shear layer to diffuse far more rapidly, thereby promoting momentum transfer toward the wall, which results in a consistently short reattachment length.},
}

@article {pmid40316668,
year = {2025},
author = {Madhwesh, N and Karanth, KV and Kumar, S},
title = {Heat transfer enhancement of a solar air heater using capsule-shaped turbulators: a numerical analysis.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {15391},
pmid = {40316668},
issn = {2045-2322},
abstract = {The development of a laminar sublayer inside the channel of the solar collector results in a poor heat transfer coefficient. Adding artificial roughness to the absorber plate in the form of turbulators is an effective and promising method of increasing heat transmission by interrupting the laminar sublayer. In this study, a capsule-shaped turbulator is used to enhance the thermal performance of the solar air heater. With flow Re (Reynolds number) fluctuating from 3000 to 21,000, the flow and heat transfer-related parameters of an air heater fitted with turbulators were numerically examined. The orientation angle of the capsule turbulator corresponding to the flow direction is modified from 0° to 90° in steps of 15°. The outcomes indicated that the overall thermal performance of the solar collector was optimized for the orientation angle of 45° at all the Reynolds numbers chosen for the study. Beyond this angle, the turbulators block the flow, increasing the pumping power. The number of rows of turbulator, pitch and height ratios of the optimized turbulator design is varied in the range of 1-3, 0.025-0.25 and 0.004-0.008, respectively, to determine their optimum values for better performance. It is observed that the turbulator having two rows with a pitch ratio of 0.05 and height ratio of 0.006 produces a relatively higher overall thermal enhancement by about 15.76% when compared with the base model without turbulators. The same configuration yields about 52.64% improvement in the exergy efficiency with respect to the base model.},
}

@article {pmid40304526,
year = {2025},
author = {Lopez, M and Kone, TC and Benchikh Le Hocine, AE and Dupont, T and Panneton, R},
title = {Mass-spring model for a perforated periodic metamaterial in nonlinear regimea).},
journal = {The Journal of the Acoustical Society of America},
volume = {157},
number = {4},
pages = {3192-3203},
doi = {10.1121/10.0036369},
pmid = {40304526},
issn = {1520-8524},
abstract = {This study is interested in the nonlinear acoustic response of a metamaterial composed of a periodic array of single-perforation plates spaced by thin air cavities. An equivalent mass-spring model is adapted to predict the metamaterial acoustic response under high sound pressure levels. The increase in losses induced by the high level is considered by a quadratic law for the airflow resistivity in an effective fluid model. The airflow resistivity coefficients are determined from predictions by the computational fluid dynamics method at different flow velocities. The model is validated with impedance tube measurements for samples with different numbers of periodic unit cells and perforation sizes. The results show that the acoustic resistance of the metamaterial increases with increasing sound pressure levels, while the reactance is almost unchanged. The absorption peaks at low frequencies are more impacted by high sound pressure levels. A criterion based on the viscous characteristic frequency is proposed to determine the limit of the beginnings of the nonlinear material response. This limit is given by an acoustic Reynolds number, which depends on the frequency and perforation size. Experimentally, an absorption peak is observed, shifting to lower frequencies with increasing sound levels. A preliminary explanation of underlying mechanisms is provided.},
}

@article {pmid40302383,
year = {2025},
author = {Shen, Z and Fu, D and Lintuvuori, JS},
title = {Inertia-driven propulsion of asymmetric spinner-dimers at moderate Reynolds numbers.},
journal = {Soft matter},
volume = {},
number = {},
pages = {},
doi = {10.1039/d5sm00108k},
pmid = {40302383},
issn = {1744-6848},
abstract = {We investigate the translational motion of rotating colloidal systems at moderate Reynolds numbers (Re), focusing on particle dimers in snowman-like configurations in three scenarios: (i) two co-rotating spheres driven by an external field, (ii) two counter-rotating spheres driven by an internal torque as a swimmer, and (iii) a single rotating spinner with a passive sphere for cargo delivery, using hydrodynamic simulations. In all three cases, the particles are bound together hydrodynamically, and the purely rotational motion of the spinners produces a net propulsion of the dimers along the axis of rotation due to symmetry breaking. We demonstrate tunable dynamics, where the propulsion direction of the co-rotating dimer can be reversed by tuning the aspect ratio and Reynolds number, as well as cargo transport where a dimer consisting of a single spinner and a passive cargo particle can have a sustained locomotion due to broken head-to-tail symmetry of the overall flow fields. These findings highlight the critical role of inertia in creating locomotion from rotational motion and offer new avenues for controlling and optimizing translational motion in colloidal assemblies through rotational degrees of freedom.},
}

@article {pmid40290984,
year = {2025},
author = {Li, F and Shao, D and Wang, Y and Wang, S and Zhang, C and Yu, M and Su, W and Rao, Y},
title = {Numerical Simulation Study on the Solid-Carrying Capacity of Hydrate-Sediment Slurry in a Vertical Pipe.},
journal = {ACS omega},
volume = {10},
number = {15},
pages = {15432-15452},
pmid = {40290984},
issn = {2470-1343},
abstract = {Solid fluidization is a green mining developed method for seabed nondiagenetic gas hydrate reservoirs, which can safely and controllably transport hydrate to land through seabed mining, closed fluidization, and gas-liquid-solid multiphase lift. However, there are many technical problems, such as hydrate and sediment fluidization and improvement of pipeline transportation capacity in the process of multiphase lift. Based on forced spiral flow in a vertical pipe, the numerical simulation of hydrate and sediment slurry in a vertical pipe with a twisted tape is carried out to explore the solid-carrying capacity of spiral flow and expand the safe boundary of multiphase flow. The effects of hydrate volume fraction, Reynolds number, hydrate particle size, and sediment particle size on turbulent kinetic energy, turbulent dissipation, solid volume fraction, and pressure of hydrate-sediment slurry have been studied. The results show that turbulent kinetic energy and turbulent dissipation decrease with the increase of hydrate volume fraction. The turbulent kinetic energy and turbulent dissipation increase with the increase of the Reynolds number. The concentration gradient of hydrate and sediment at the outlet section is larger than that of the horizontal spiral pipe. The hydrate particle volume fraction at the hydrate axis increases with the increase of hydrate volume fraction, Reynolds number, and hydrate particle size. Sediment particles are mainly distributed near the pipe wall, and hydrate particles are mainly distributed on the inner side of the sediment and form a high-concentration ring. The pressure change in the vertical pipe is similar to that in the horizontal pipe. When Re = 30,000, the critical volume fraction of hydrate blockage in the vertical pipe is 47%, while the critical volume fraction is 22% in the vertical smooth pipe. The transport capacity of hydrate particles is increased by 1.14 times. Under the same conditions, the pressure drop of the whole pipe exceeds that of the ordinary smooth pipe by about 15%.},
}

@article {pmid40287521,
year = {2025},
author = {Kunal, and Dhiman, SK},
title = {An experimental study on effect of curvatures of upstream tube on thermal performance of downstream tube in cross-flow of air.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {14669},
pmid = {40287521},
issn = {2045-2322},
abstract = {Heat transfer on a straight tube in the wake of a tube of same diameter with different curvatures was investigated in cross-flow of air at Reynolds number of 35,000. The straight tube was given constant heat flux condition and placed at different spacing ratios of 2.0, 2.25, 2.5, 3.0, 3.5, and 4.0, from the curved tubes at blockage ratio of 0.1. Four different curvatures ratios 0.5, 1.0, 1.5 and 2.0, on curved tubes were given which were aligned with the mainstream as concave and convex profiles forming different combinations of curvature ratios and spacing ratios to analyse their thermal performance. The study shows a paramount advantage of enhanced thermal performance using curved tube combinations over straight tube combinations and identifies a Reynolds number-based inflection point describing "Heat Promoter" as upstream segment of the tube. The results illustrate that concave curved combination with curvature ratio 1.0 at spacing ratio 2.5 exhibited highest thermal performance with 2.36 times enhanced heat transfer.},
}

@article {pmid40283266,
year = {2025},
author = {Hou, Y and Hu, M and Sun, D and Sun, Y},
title = {Numerical Simulation in Microvessels for the Design of Drug Carriers with the Immersed Boundary-Lattice Boltzmann Method.},
journal = {Micromachines},
volume = {16},
number = {4},
pages = {},
doi = {10.3390/mi16040389},
pmid = {40283266},
issn = {2072-666X},
support = {52301035//National Natural Science Foundation of China/ ; BK20230844//Natural Science Foundation of Jiangsu Province/ ; },
abstract = {This study employs numerical techniques to investigate the motion characteristics of red blood cells (RBCs) and drug carriers (DCs) within microvessels. A coupled model of the lattice Boltzmann method (LBM) and immersed boundary method (IBM) is proposed to investigate the migration of particles in blood flow. The lattice Bhatnagar-Gross-Krook (LBGK) model is utilized to simulate the flow dynamics of blood. While the IBM is employed to simulate the motion of particles, using a membrane model based on the finite element method. The present model was validated and demonstrated good agreements with previous theoretical and numerical results. Our study mainly examines the impact of the Reynolds number, DC size, and stiffness. Results suggest that these factors would influence particles' equilibrium regions, motion stability and interactions between RBCs and DCs. Within a certain range, under a higher Reynolds number, the motion of DCs remains stable and DCs can swiftly attain their equilibrium states. DCs with smaller sizes and softer stiffness demonstrate a relatively stable motion state and their interactions with RBCs are weakened. The findings would offer novel perspectives on drug transport mechanisms and the impact of drug release, providing valuable guidance for the design of DCs.},
}

@article {pmid40281346,
year = {2025},
author = {Ali, N and Sajid, M},
title = {Inertial swimming in an Oldroyd-B fluid.},
journal = {The European physical journal. E, Soft matter},
volume = {48},
number = {4-5},
pages = {19},
pmid = {40281346},
issn = {1292-895X},
abstract = {The effects of fluid inertia on a self-propelling inextensible waving sheet in an Oldroyd-B fluid are examined. The swimming velocity of the sheet is calculated in the limit in which the amplitude of the waves propagating along the sheet is small relative to the wavelength of the waves. The rate of work done by the sheet is also calculated. It is found that the swimming speed decreases monotonically approaching a limiting value with increasing Reynolds number (R) for a Newtonian fluid. For an Oldroyd-B fluid, the swimming speed increases to a maximum and then decreases asymptotically to a limiting value with increasing R. In contrast, it increases monotonically to a limiting value with increasing R for a Maxwell fluid. The limiting value is highest for the Maxwell fluid and lowest for the Oldroyd-B fluid. The corresponding value for the Newtonian fluid lies in between. The rate of work done by the sheet increases with increasing Reynolds number for all Deborah numbers. However, the energy consumed at a fixed swimming speed is lesser for an Oldroyd-B fluid than that of a Newtonian fluid. These results suggest that contrary to the Newtonian case, the fluid inertia supports the swimming sheet motion in a complex fluid. At a particular Deborah number, the oscillation frequency of the sheet could be adjusted to achieve the maximum speed. Similarly, at a particular frequency of oscillation, the Deborah numbers could be adjusted to achieve the maximum speed. These observations are in sharp contrast with the previous results reported for Newtonian and second-order fluids.},
}

@article {pmid40276589,
year = {2025},
author = {Suzuki, K and Nakane, D and Mizutani, M and Nishizaka, T},
title = {Gliding direction of Mycoplasma mobile correlates with the curved configuration of its cell shape.},
journal = {Biophysics and physicobiology},
volume = {22},
number = {1},
pages = {e220006},
pmid = {40276589},
issn = {2189-4779},
abstract = {The gliding motility of bacteria is not linear but somehow exhibits a curved trajectory. This general observation is explained by the helical structure of protein tracks (Nakane et al., 2013) or the asymmetric array of gliding machineries (Morio et al., 2016), but these interpretations have not been directly examined. Here, we introduced a simple assumption: the gliding trajectory of M. mobile is guided by the cell shape. To test this idea, the intensity profile of a bacterium, Mycoplasma mobile, was analyzed and reconstructed at the single-cell level from images captured under a highly stable dark-field microscope, which minimized the mechanical drift and noise during sequential image recording. The raw image with the size of ~1 μm, which is about four times larger than the diffraction limit of visible light, was successfully fitted by double Gaussians to quantitatively determine the curved configuration of its shape. By comparing the shape and curvature of a gliding motility, we found that the protruded portion of M. mobile correlated with, or possibly guided, its gliding direction. Considering the balance between decomposed gliding force and torque as a drag, a simple and general model that explains the curved trajectory of biomolecules under a low Reynolds number is proposed.},
}

@article {pmid40274926,
year = {2025},
author = {Dey, R and Patni, HK and Anand, S},
title = {Improved aerosol deposition predictions in human upper respiratory tract using coupled mesh phantom-based computational model.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {14260},
pmid = {40274926},
issn = {2045-2322},
abstract = {Aerosol deposition in the human respiratory tract significantly impacts drug delivery, pollutant exposure, and radiological protection. While existing models, such as the Multiple-Path Particle Dosimetry (MPPD) and the Human Respiratory Tract Model (HRTM) from International Commission on Radiological Protection (ICRP) provide valuable insights, their reliance on simplified geometries and flow dynamics, limits their ability to accurately predict particle deposition within realistic anatomies. This study integrates Mesh-type Reference Computational Phantoms (MRCPs) with computational fluid-particle dynamics (CFPD) to address these limitations. Our simulations reveal the influence of complex anatomical features, including nasal cavity, trachea, and bronchial regions, on aerosol deposition patterns. For ambient aerosol particles in the diffusion-dominated regime (< 0.5 μm), CFPD results reveal enhanced nasal deposition fractions than ICRP predictions, while, above this size, the ICRP semi-empirical model shows overestimations. In the extrathoracic (ET) airways, deposition distribution varied significantly between ET1 and ET2, with ET2 receiving 65-75% of deposits (near the junction of ET1 and ET2) under certain flow conditions. In the bronchial bifurcation (BB1), deposition efficiency varies with Stokes number and Reynolds number, revealing localized preferential deposition. These findings enhance our understanding of aerosol behaviour and paves the way for more accurate therapeutic and safety models in radiological protection.},
}

@article {pmid40274905,
year = {2025},
author = {Boudet, JF and Bergmann, M and Iollo, A and Kellay, H},
title = {Effects of boundaries for high Reynolds number artificial swimmers.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {14264},
pmid = {40274905},
issn = {2045-2322},
support = {ANR-22-CE06-0007-02.//Agence Nationale de la Recherche/ ; ANR-22-CE06-0007-02.//Agence Nationale de la Recherche/ ; },
abstract = {The spatial organization of active particles or swimmers may depend strongly on the nature of the interaction between the particles and the boundary. Here we use robotic fish of several centimeters dimensions that swim at high enough velocities to reach Reynolds numbers Re of order [Formula: see text] or [Formula: see text]. Under confinement in circular arenas filled with a shallow layer of water, these robots swim mostly near the walls and undergo a gradual transition from swirling motion near the boundaries to large cluster formation as the number of particles in the assembly is increased. This transition is highly dependent on the nature of the walls: for solid impermeable walls this transition occurs for small numbers of fish robots. For porous walls this transition is delayed and occurs at larger numbers. The main reason why the two boundaries affect the swimming differently is the alignment of the fish robots at the wall: for the impermeable boundary the fish robots align with a smaller angle to the wall while for the porous case, the fish robots align with a larger angle at the wall allowing the formation of linear clusters. We carry out numerical simulations of model fish in three dimensions to examine how such experimental results can be understood. The interest of these simulations is that they provide a direct and quantitative view of the properties of the flow engendered by the fish like objects. The interaction of this flow with other fish or with the boundaries is the crucial aspect behind the self organization. These simulations reproduce the main features of the behavior of the swimmers such as their swimming near the walls or their angle with respect to the boundary. By using flexible and free to move arenas in experiments and simulations, we show that the assembly of fish robots is capable of creating large deformations as well as induce mobility of the arenas through the self-organization of the robotic fish opening the possibility of making sub-aquatic flexible robots of robots.},
}

@article {pmid40273102,
year = {2025},
author = {Chen, X and Sreenivasan, KR},
title = {Bounded dissipation law and profiles of turbulent velocity moments in wall flows.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {122},
number = {17},
pages = {e2502265122},
doi = {10.1073/pnas.2502265122},
pmid = {40273102},
issn = {1091-6490},
support = {92252201 12072012//National Science Foundation of China/ ; None//NYU | Tandon School of Engineering, New York University (Tandon)/ ; },
abstract = {Understanding the effects of solid boundaries on turbulent fluctuations remains a long-standing challenge. Available data on mean-square fluctuations in these flows show apparent contradiction with classical scaling. We had earlier proposed an alternative model based on the principle of bounded dissipation. Despite its putative success, a conclusive outcome requires much higher Reynolds numbers than are available at present, or can be expected to be available in the near future. However, the model can be validated satisfactorily even within the Reynolds number range already available by considering high-order moments and their distributions in the wall-normal direction. Expressions for high-order moments of streamwise velocity fluctuation [Formula: see text] are derived in the form [Formula: see text], where the superscript [Formula: see text] indicates the wall unit normalization, and brackets stand for averages over time and the homogeneous plane normal to the wall, [Formula: see text] is an integer, [Formula: see text] and [Formula: see text] are constants independent of the friction Reynolds number [Formula: see text], and [Formula: see text] is the distance away from the wall, normalized by the flow thickness [Formula: see text]. In particular, [Formula: see text] according to the "linear q-norm Gaussian" process, where [Formula: see text] and [Formula: see text] are flow-independent constants. Excellent agreement is found between this formula and the available data in boundary layers, pipes, and channels for [Formula: see text]. For fixed [Formula: see text], the present formulation leads to the bounded state [Formula: see text] as [Formula: see text]. This work demonstrates the success of the present model in describing the behavior of fluctuations in wall flows.},
}

@article {pmid40269237,
year = {2025},
author = {Bhattacharyya, S and Vishwakarma, DK},
title = {Mixed and forced convection heat transfer and pressure drop in inclined tube with twisted tape in transition flow.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {14018},
pmid = {40269237},
issn = {2045-2322},
abstract = {Understanding the influence of angular orientation on mixed convection heat transfer and pressure drop in circular tubes with swirl generators is crucial for optimizing thermal performance in various engineering applications, including heat exchangers and energy systems. This study aims to investigate the impact of angular orientation on heat transfer enhancement and pressure drop characteristics in a uniformly heated circular tube equipped with a twisted-tape longitudinal swirl generator. An experimental approach was employed, varying key parameters such as Reynolds number (435-10,130), heat flux (2, 3, and 4 kW/m[2]), twist ratio (P/D = 3, 4, and 5), and angular orientation (15° and 30°). The setup was validated against established correlations for Nusselt number and friction factor, demonstrating strong agreement. The results reveal that angular orientation significantly affects heat transfer and pressure drop at Reynolds numbers up to ~ 1000, where mixed convection plays a dominant role. Beyond this, forced convection prevails. In a plain channel, the transition from laminar to transitional flow occurs at Reynolds numbers of 2924-4088 for a 15° angle of inclination (AoI) and 3001-4274 for a 30° AoI, with the transition occurring slightly earlier at the lower angle. The Richardson number varied from 2.5 in the low laminar regime to 0.0087 in the turbulent regime, with additional variations observed when turbulators were introduced.},
}

@article {pmid40269048,
year = {2025},
author = {Kaziz, S and Echouchene, F and Gazzah, MH},
title = {Optimizing microfluidic chip for rapid SARS-CoV-2 detection using Taguchi method and artificial neural network PSO.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {14052},
pmid = {40269048},
issn = {2045-2322},
mesh = {*Neural Networks, Computer ; *SARS-CoV-2/isolation & purification ; *COVID-19/diagnosis/virology ; Humans ; *Biosensing Techniques/methods/instrumentation ; *Lab-On-A-Chip Devices ; },
abstract = {Microfluidic biosensors offer a promising solution for real-time analysis of coronaviruses with minimal sample volumes. This study optimizes a biochip for the rapid detection of SARS-CoV-2 using the Taguchi orthogonal table L9(3[4]), which comprises nine groups of experiments varying four key parameters: Reynolds number (Re), Damköhler number (Da), Schmidt number (Sc), and the dimensionless position of the reaction surface (X). Signal-to-noise (S/N) ratios and analysis of variance (ANOVA) are employed to determine optimal parameters and assess their impact on binding kinetics and response time of the detection device. These obtained optimal parameters correspond to Re = 4.10[-2], Da = 1000, Sc = 10[5], and X = 1. Additionally, results highlight Da as the most influential factor, accounting for 91%, while X has a minimal effect of 0.3%. Furthermore, an artificial neural network optimization technique, specifically particle swarm optimization (PSO), was utilized to predict biosensor performance. Derived from the Full L81(3[4]) design experiment, the PSO model demonstrates its effectiveness compared to the conventional multi-layer perception (MLP) model, thus underlining its potential in this innovative optimization context.},
}

*Neural Networks, Computer
*SARS-CoV-2/isolation & purification
*COVID-19/diagnosis/virology
Humans
*Biosensing Techniques/methods/instrumentation
*Lab-On-A-Chip Devices

@article {pmid40262639,
year = {2025},
author = {Yaqoob, B and Porfiri, M and Pugno, NM},
title = {Optimizing energetics of lateral undulatory locomotion: unveiling morphological adaptations in different environments.},
journal = {Journal of the Royal Society, Interface},
volume = {22},
number = {225},
pages = {20240440},
doi = {10.1098/rsif.2024.0440},
pmid = {40262639},
issn = {1742-5662},
support = {//Italian Ministry of Education, University and Research (MIUR)/ ; //National Science Foundation/ ; },
abstract = {Ongoing efforts seek to unravel theories that can make simple, quantitative and reasonably accurate predictions of the morphological adaptive changes that arise with the size variation. Yet, relatively scant attention has been directed towards lateral undulatory locomotion. In the current study, we explore: (i) the constraints imposed by the variation of length and mass in viscous and dry friction environments on the cost of transport (COT) of lateral undulatory locomotion and (ii) the role of the body, environment and input oscillations in such an intricate interplay. In a dry friction environment, minimum COT correlates with stiffer and longer bodies, higher frictional anisotropy and angular amplitudes greater than approximately 10[o]. Conversely, a viscous environment favours flexible long bodies, higher frictional anisotropy and angular amplitudes lower than approximately 30[o]. In both environments, optimizing mass and maintaining low angular frequencies minimizes COT. Our conclusions are applicable only in the low-Reynolds-number regime, and it is essential to consider the interdependence of parameters when applying the generalized results. Our findings highlight musculoskeletal and biomechanical adaptations that animals may use to mitigate the consequences of size variation and to meet the energetic demands of lateral undulatory locomotion. These insights enhance foundational biomechanics knowledge while offering practical applications in robotics and ecology.},
}

@article {pmid40256679,
year = {2025},
author = {Shankaran, A and Hearst, RJ},
title = {Simultaneous measurements of velocity, oxygen concentration, and deformed interface position in an air-water channel using PIV and LIF.},
journal = {Experiments in fluids},
volume = {66},
number = {5},
pages = {95},
pmid = {40256679},
issn = {0723-4864},
abstract = {Oxygen transfer across a deforming air-water interface is studied using a synergy of particle image velocimetry and laser-induced fluorescence (LIF). Such approaches have previously been limited to flat interfaces. We develop simultaneous measurements of velocity fields, dissolved oxygen (DO) concentration fields, and interface positions for spatial and temporal tracking. The imaging process begins after the DO in the water has been chemically depleted and continues until the water is saturated with DO. The oxygen LIF intensity field is calibrated using measurements from an optical oxygen probe to ensure accurate conversion into physical unit (mg/L). A canonical air turbulent channel flow, with a centerline velocity of 6.6 m/s (Reynolds number based on channel height of 21,700), develops for more than 100 heights before the bottom boundary condition is changed from a solid wall to a water surface. This induces transient and wavy structures on the air-water interface and generates velocity fluctuations and vorticity on the water side, which drives DO transport. The spatial evolution of DO concentration reveals steep gradients near the interface that diminish with depth, while the temporal evolution shows a reduction in concentration differences between the bulk and interface from about 35% to less than 5% as the water saturates. Concentration fluctuations are lower near the interface compared to the bulk and diminish in time as the system approaches saturation. Turbulent scalar transport analysis shows high vertical flux near the interface, and this too changes as the bulk DO concentration evolves, emphasizing that the observed phenomena are transient and should be treated as such.},
}

@article {pmid40250393,
year = {2025},
author = {Wang, Y and Ebrahimi, F and Lu, H and Goodman, J and Gilson, EP and Ji, H},
title = {Observation of Nonaxisymmetric Standard Magnetorotational Instability Induced by a Free-Shear Layer.},
journal = {Physical review letters},
volume = {134},
number = {13},
pages = {135101},
doi = {10.1103/PhysRevLett.134.135101},
pmid = {40250393},
issn = {1079-7114},
abstract = {The standard magnetorotational instability (SMRI) with a magnetic field component parallel to the rotation axis is widely believed to be responsible for the fast accretion in astronomical disks. In conventional base flows with a Keplerian profile or an ideal Couette profile, most studies focus on axisymmetric SMRI, since excitation of nonaxisymmetric SMRI in such flows requires a magnetic Reynolds number (Rm) more than an order of magnitude larger. Here, we report that, in a magnetized Taylor-Couette flow, nonaxisymmetric SMRI with an azimuthal mode number m=1 can be triggered by a free-shear layer in the base flow at Rm≳1, the same threshold as for axisymmetric SMRI. Global linear analysis reveals that the free-shear layer reduces the required Rm, possibly by introducing an extremum in the vorticity of the base flow. Nonlinear simulations validate the results from linear analysis and confirm that a novel instability recently discovered experimentally [Wang et al., Nat. Commun. 13, 4679 (2022)NCAOBW2041-172310.1038/s41467-022-32278-0] is the nonaxisymmetric m=1 SMRI. Our finding has astronomical implications as free-shear layers are ubiquitous in celestial systems, such as the disk-star boundary layer, the solar tachocline, and the edge of planet-opened gaps in protoplanetary disks.},
}

@article {pmid40225806,
year = {2025},
author = {Kavitha, R and Ladu, NSD and Ravi, S},
title = {Soret Effect and Chemical Process on MHD Oscillatory Flow in a Physiological Fluid.},
journal = {Applied bionics and biomechanics},
volume = {2025},
number = {},
pages = {8818822},
pmid = {40225806},
issn = {1176-2322},
abstract = {This paper investigates the impact of chemical and Soret reactions on magnetohydrodynamic (MHD) oscillatory flow in a porous arteriole. Using appropriate mathematical techniques, a model of a mathematical equation is developed and solved. The flow governing equations are formulated based on certain assumptions. Exact solutions are attained for the profiles of velocity, temperature, and concentration. To highlight the key features, the numerical computations of the physical parameters, Grashof number, Reynolds number, Magnetic number, and Soret number were presented graphically. The present study reveals the viscoelasticity of blood significantly reduces flow velocity. And also illustrates blood flow (BF) in the artery is affected by the Lorentz force, which causes the velocity of the BF to increase as the magnetic field parameter values increase. The obtained outcome may be very useful in controlling BF during the surgical procedure.},
}

@article {pmid40224519,
year = {2025},
author = {Jayatilake, S and Lowenberg, M and Woods, BKS and Titurus, B},
title = {Nonlinear aeroelastic modelling and analysis of a geometrically nonlinear wing with combined unsteady sectional and lifting line aerodynamics.},
journal = {Nonlinear dynamics},
volume = {113},
number = {12},
pages = {14657-14693},
pmid = {40224519},
issn = {0924-090X},
abstract = {This research develops a novel geometrically nonlinear aeroelastic model of a cantilevered flexible wing capable of capturing unsteady aerodynamics with finite span effects. The structural model is developed using a Chebyshev-Ritz approach with the ONERA unsteady aerodynamic formulation coupled to a three-dimensional wing analysis based on the lifting line approach. The resulting system describing the evolution of the generalised structural coordinates and the aerodynamic states is formulated as a continuous state space model. The model is validated against experimental results from the wind tunnel testing of a highly flexible wing demonstrator at the University of Bristol. The numerical results are computed by applying a numerical continuation procedure, exercising the benefits of the state space formulation. The extensive numerical-experimental comparative analysis includes the bifurcation characteristics of the system and the behaviour of the aeroelastic modes. The developed model reflected the experimentally identified bifurcation behaviour. The predicted variations of the flutter onset speed with the wing root pitch angles were found to be within 5% of the experimental values. The model also correctly captured the post-flutter Limit Cycle Oscillation (LCO). This work further showed that the predicted flutter speeds are sensitive to the semi-empirical coefficients present in the ONERA unsteady aerodynamics formulation. Consequently, further calibration of the model was based on the analysis of the experimental flutter speeds and airspeed-driven eigenvalue variations. This approach was necessitated by the influence of application-specific conditions (e.g., the Reynolds number) on the unsteady aerodynamic characteristics. Despite this limitation, the tuned model agreed with the experimental observations across a wide range of test conditions. The approaches presented in this work can benefit multiple applications during research on geometrically nonlinear wings, such as the analysis of root causes influencing critical aeroelastic phenomena or design of aeroelastic control laws.},
}

@article {pmid40209649,
year = {2025},
author = {Zhu, F and Hu, X and Wu, X and Xu, D and Li, Q and Chen, X and Pang, W and Duan, X and Wang, Y and He, M},
title = {Synergistic effect of acoustic streaming and nanozymes on enhanced intracellular dopamine detection.},
journal = {Biosensors & bioelectronics},
volume = {280},
number = {},
pages = {117431},
doi = {10.1016/j.bios.2025.117431},
pmid = {40209649},
issn = {1873-4235},
abstract = {Microfluidic electrochemical biosensing has been widely recognized, but it suffers the slow mass transfer caused by low Reynolds number in the microenvironment. This work proposes a multifunctional portable microfluidic electrochemical platform integrated with a gigahertz acoustic resonator, achieving improved electrochemical response, in situ nanozymes modification, cellular pre-treatment and portable detection on one chip. It was observed that the acoustic streaming (AS) generated by the resonator could reduce the thickness of the double electric diffusion layer and improve the mass transfer in bulk solution, leading to an enhancement in microfluidic electrochemical current response. In addition, in situ electrodeposition of polypyrrole (Ppy) and Ni3(HHTP)2 nano-composite nanozymes (Ppy-Ni3(HHTP)2) was achieved to increase the electrocatalytic activity of dopamine (DA). The results further revealed that AS and Ppy-Ni3(HHTP)2 collectively enhance the electrochemical detection of DA. Moreover, cell pre-treatment and intracellular DA detection was achieved to distinguish the passage of dopaminergic cells by the microfluidic electrochemical platform. Finally, portable detection of intracellular dopamine was realized by integrating the platform with the portable electrochemical sensing system. This study presented a novel approach to collectively enhance electrochemical biosensing using AS and nanozymes.},
}

@article {pmid40206413,
year = {2018},
author = {Brindise, MC and Vlachos, PP},
title = {Pulsatile pipe flow transition: Flow waveform effects.},
journal = {Physics of fluids (Woodbury, N.Y. : 1994)},
volume = {30},
number = {1},
pages = {},
pmid = {40206413},
issn = {1070-6631},
abstract = {Although transition is known to exist in various hemodynamic environments, the mechanisms that govern this flow regime and their subsequent effects on biological parameters are not well understood. Previous studies have investigated transition in pulsatile pipe flow using non-physiological sinusoidal waveforms at various Womersley numbers but have produced conflicting results, and multiple input waveform shapes have yet to be explored. In this work, we investigate the effect of the input pulsatile waveform shape on the mechanisms that drive the onset and development of transition using particle image velocimetry, three pulsatile waveforms, and six mean Reynolds numbers. The turbulent kinetic energy budget including dissipation rate, production, and pressure diffusion was computed. The results show that the waveform with a longer deceleration phase duration induced the earliest onset of transition, while the waveform with a longer acceleration period delayed the onset of transition. In accord with the findings of prior studies, for all test cases, turbulence was observed to be produced at the wall and either dissipated or redistributed into the core flow by pressure waves, depending on the mean Reynolds number. Turbulent production increased with increasing temporal velocity gradients until an asymptotic limit was reached. The turbulence dissipation rate was shown to be independent of mean Reynolds number, but a relationship between the temporal gradients of the input velocity waveform and the rate of turbulence dissipation was found. In general, these results demonstrated that the shape of the input pulsatile waveform directly affected the onset and development of transition.},
}

@article {pmid40199959,
year = {2025},
author = {Khan, SH and Danish, M and Ayaz, M and Husain, A and Saeed, S and Abdulla, S and Shaheen, S and Saeed, A and Thaher, A},
title = {Aerodynamic analysis and ANN-based optimization of NACA airfoils for enhanced UAV performance.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {11998},
pmid = {40199959},
issn = {2045-2322},
support = {G00004417//Research Office at UAE University/ ; G00004417//Research Office at UAE University/ ; G00004417//Research Office at UAE University/ ; G00004501//College of Graduate Studies, United Arab Emirates University/ ; },
abstract = {The performance of unmanned aerial vehicles (UAVs) is strongly dependent on the design of their airfoils, particularly in applications necessitating high maneuverability, stability, and efficiency. This study analyzed three National Advisory Committee for Aeronautics (NACA) airfoil profiles: NACA 2412, NACA 4415, and NACA 0012, using a combination of computational fluid dynamics (CFD), XFOIL simulations, and a hybrid artificial neural network-genetic algorithm (ANN-GA) model. This study aimed to evaluate and optimize the aerodynamic performance of these airfoils under various flight conditions. Through CFD simulations and XFOIL analysis, we explored the lift, drag, and stall characteristics of each airfoil at different angles of attack and Reynolds numbers. The NACA 4415 airfoil consistently outperformed the others, achieving the highest lift-to-drag ratio ([Formula: see text]) and exhibiting favorable stall behavior. Thus, it is particularly well-suited for UAVs operating in challenging environments. Further, streamline and velocity profile analyses confirmed that NACA 4415 exhibited a smooth airflow and delayed flow separation, thereby contributing to its superior aerodynamic efficiency. Using the hybrid ANN-GA model, we optimized key parameters, such as the angle of attack and Reynolds number with optimal values of [Formula: see text] and 770,801, respectively, for maximum efficiency. Additionally, the ANN model demonstrated a high accuracy in predicting the aerodynamic performance, closely matching the results of the CFD simulations. Overall, this study highlighted the potential of combining computational techniques and machine- learning models to optimize UAV airfoil designs. These findings offer valuable insights for improving the efficiency and agility of UAVs, particularly in industries such as precision agriculture, infrastructure inspection, and environmental monitoring.},
}

@article {pmid40199935,
year = {2025},
author = {Dong, L and Zhang, R},
title = {Numerical study on falling film flow outside the refrigerant tube.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {11952},
doi = {10.1038/s41598-025-96057-9},
pmid = {40199935},
issn = {2045-2322},
support = {2023ZR04//Natural Science Foundation of Dongying/ ; 2024ZDJH75//Dongying City Science and Technology Innovation Major Project (Science and Technology Development Guidance Scheme)/ ; DJ2023004//Science Development Funding Program of Dongying of China/ ; },
abstract = {The liquefied natural gas (LNG) floating production storage and offloading (FPSO) unit is a new type of floating production device developed for the exploitation, pretreatment, liquefaction, and storage of offshore natural gas. In this study, the shell side structure of the spiral-wound heat exchanger is analyzed, and the effects of varying the Reynolds number (Re), tube outer diameter, and number of distributors on the thickness of the shell-side liquid film are investigated. The results show that as the fluid flows down from the distributor, it hits the upper wall of the pipeline and diffuses evenly to both sides, before converging in between the two distributors. In the axial direction, the thickness of the liquid film increases first, reaches the highest at the peak, then decreases, reaches the lowest at the trough, and then increases again, forming a secondary peak at the drop. The thickness of the liquid film changes periodically, and the period is the distance between the two distributors. The thickness of the circumferential liquid film is negatively correlated with the circumferential angle, α. Moreover, the liquid film is thinnest at α = 120°, and is positively correlated with both the liquid mass flow rate and the outer diameter of the tube. The most uniform liquid film thickness is obtained when Re = 1500, the tube outer diameter is 12 mm, and the number of distributors is 6. The results from this study can guide the design of spiral-wound heat exchangers and facilitate their safe and efficient operation in natural gas liquefaction processes.},
}

@article {pmid40183380,
year = {2025},
author = {Qin, L and Liu, X and Fei, F},
title = {CFD-Based Optimization of a Dielectrophoretic Device to Isolate CTCs.},
journal = {Electrophoresis},
volume = {},
number = {},
pages = {},
doi = {10.1002/elps.8129},
pmid = {40183380},
issn = {1522-2683},
support = {2024B05//Open Project of Key Laboratory of Education/ ; },
abstract = {Cancer cells that have separated from the main tumor and entered the bloodstream are known as circulating tumor cells (CTCs). Once there, they may spread to other parts of the body and cause metastases. This work proposes a novel inertial-based dielectrophoresis (DEP) device designed for the separation of CTCs from red blood cells (RBCs). The microchannel features a rectangular zigzag segment combined with a circular curved section, optimized to improve separation efficiency by integrating inertial and DEP forces. Numerical simulations are conducted to evaluate the effects of microchannel depth, applied voltage and frequency, and Reynolds number (Re) on the separation efficiency and trajectory of cells. The simulations identify four optimal scenarios that achieve 100% separation efficiency. Early cancer diagnosis and treatment may benefit from the use of the proposed device for CTC detection.},
}

@article {pmid40177117,
year = {2025},
author = {Clemens, AL and Jung, K and Ferrucci, M and Ellis, ME and Davis, JT and Chandrasekaran, S and Qi, Z and Orme, CA and Worsley, MA and Akolkar, R and Ivanovskaya, A and Dudukovic, NA},
title = {Understanding the Current Distribution and Mass Transport Properties in 3D-Printed Architected Flow-Through Electrodes.},
journal = {ACS applied engineering materials},
volume = {3},
number = {3},
pages = {600-612},
doi = {10.1021/acsaenm.4c00561},
pmid = {40177117},
issn = {2771-9545},
abstract = {Architected materials offer promising advancements in energy storage by enabling highly customizable, high-surface-area, ordered, and low-defect porous structures. This study investigates the current distribution and mass transport within complex 3D-printed lattice electrodes under flow-through conditions. Conductive lattices were fabricated using microstereolithography followed by pyrolytic carbonization. Lattice geometry effects were analyzed by varying the unit cell type [simple cubic (SC), body- and face-centered cubic (BCC/FCC), IsoTruss, and Octet], porosity, and current density. Current distribution uniformity was investigated using a model high-efficiency copper deposition reaction. Local film thickness distributions were predicted using a numerical model and validated experimentally using micro-X-ray computed tomography. Scaling relationships for informing electrochemical reaction conditions and current uniformity are formulated as a modified lattice-based Wagner number (Wa Lattice) and a corresponding inverse Damkohler number (Da Lattice [-1]). Validated models reveal that mass-transfer coefficients scale as Octet > IsoTruss > FCC ∼ BCC > SC. Inertial effects become significant at Reynolds number Re > 3 and are particularly pronounced in Octet structures due to an abundance of struts oriented away from the fluid flow direction. The study underscores the importance of electrode engineering and process conditions necessary to tailor mass transport and current uniformities to various device applications.},
}

@article {pmid40167398,
year = {2025},
author = {Zhang, P and Wang, Y and Wang, Y},
title = {Development of pulse-type skin friction balance use in shock tunnel.},
journal = {The Review of scientific instruments},
volume = {96},
number = {4},
pages = {},
doi = {10.1063/5.0246911},
pmid = {40167398},
issn = {1089-7623},
abstract = {The wall shear stress significantly affects the aerodynamic characteristics and flight safety of hypersonic aircraft. More accurate and reliable diagnostic instruments are required to fully understand and optimize the distribution of wall shear stress in hypersonic high-enthalpy flow. Two types of assembled and integrated skin friction balances for high-enthalpy impulse facilities were developed. The integrated balance was processed using additive manufacturing, also known as 3D printing. The static calibration uncertainty of the two types of skin friction balances is lower than 0.2% FS at 95% confidence. The first-order vibration frequency is about 50 Hz. The applicability and reliability of the developed skin friction balance were verified in the JF-12 shock tunnel built by the Institute of Mechanics, Chinese Academy of Sciences. A series of wall shear measurement tests for flat-plate boundary layers were carried out, in a freestream with a nominal Mach number of 7 and a unit Reynolds number of about 106. The wall shear results were in good agreement with the numerical simulation and empirical formula results. The minimum deviation can reach 3.67% of the measured value, which verifies the applicability and reliability of the two types of skin friction balances for accurate wall shear stress in high-enthalpy pulse flow, especially providing experimental support for the feasibility of the additive-manufactured balance.},
}

@article {pmid40160717,
year = {2025},
author = {Turkevich, LA and Chen, H and Jog, MA},
title = {Dust resuspension from the splash of a falling powder: A numerical aerodynamic simulation of a pellet falling onto a powder monolayer.},
journal = {Aerosol science and technology : the journal of the American Association for Aerosol Research},
volume = {59},
number = {1},
pages = {49-65},
doi = {10.1080/02786826.2024.2417976},
pmid = {40160717},
issn = {0278-6826},
abstract = {A falling powder can generate a dust cloud from its interaction with the ambient air and from its splash onto a substrate. This article reports the results of a numerical simulation study, which attempts to model this second process. We argue that the dust cloud arises from the aerodynamic resuspension of previously deposited small particles. The agglomerated falling powder is modeled as a falling pellet disk impacting a surface covered with a monolayer of previously deposited particles. The Reynolds number of the air flow in the vicinity of the impacting pellet is Re ~ 1860, so the air flow is modeled as laminar and incompressible. The dust particles are incorporated via a Lagrangian multiphase treatment. The sudden deceleration of the disk sheds an aerodynamic vortex, which suspends particles from the monolayer. Characteristics of the dust cloud (average and maximum height and radius) are tracked; these are conveniently summarized by following the trajectory of the dust cloud centroid. The probability of aerosolization decreases with distance from the impacted pellet. The centroid trajectory is studied as a function of dust particle size. The model is relatively insensitive to disk radius and thickness. More realistic modeling of dust clouds generated by the splash of falling powders will require a statistical analysis of aggregate size and location, as well as the inclusion of interparticle and particle-surface interactions.},
}

@article {pmid40153508,
year = {2025},
author = {Sui, F and Yue, W and Behrouzi, K and Gao, Y and Mueller, M and Lin, L},
title = {Untethered subcentimeter flying robots.},
journal = {Science advances},
volume = {11},
number = {13},
pages = {eads6858},
doi = {10.1126/sciadv.ads6858},
pmid = {40153508},
issn = {2375-2548},
abstract = {The miniaturization of insect-scale flying robots with untethered flights is extremely challenging as the tradeoff between mass and power becomes problematic. Here, a subcentimeter rotating-wing robot of 21 mg in weight and 9.4 mm in wingspan driven by a single-axis alternating magnetic field has accomplished navigable flights. This artificial flying robot is the lightest and smallest to realize untethered and controllable aerial travels including hovering, collision recovery, and route adjustments. Experimentally, it has achieved a high aerodynamic efficacy with a measured lift-to-drag ratio of 0.7 and lift-to-flying power ratio of 7.2 × 10[-2] N/W at a Reynolds number of ~2500. The wireless driving mechanism, system operation principle, and flight characteristics can be further optimized for the advancement and miniaturization of subcentimeter scale flying robots.},
}

@article {pmid40152021,
year = {2025},
author = {Kuddushi, M and Kanike, C and Xu, BB and Zhang, X},
title = {Recent advances in nanoprecipitation: from mechanistic insights to applications in nanomaterial synthesis.},
journal = {Soft matter},
volume = {},
number = {},
pages = {},
doi = {10.1039/d5sm00006h},
pmid = {40152021},
issn = {1744-6848},
abstract = {Nanoprecipitation is a versatile, low-energy technique for synthesizing nanomaterials through controlled precipitation, enabling precise tuning of material properties. This review offers a comprehensive and up-to-date perspective on nanoprecipitation, focusing on its role in nanoparticle synthesis and its adaptability in designing diverse nanostructures. The review begins with the foundational principles of nanoprecipitation, emphasizing the impact of key parameters such as flow rate, mixing approach, injection rate, and Reynolds number on nanomaterial characteristics. It also discusses the influence of physicochemical factors, including solvent choice, polymer type, and drug properties. Various nanoprecipitation configurations-batch, flash, and microfluidic are examined for their specific advantages in controlling particle size, morphology, and internal structure. The review further explores the potential of nanoprecipitation to create complex nanostructures, such as core-shell particles, Janus nanoparticles, and porous and semiconducting polymer nanoparticles. Applications in biomedicine and other fields highlight nanoprecipitation's promise as a sustainable and tunable method for fabricating advanced nanomaterials. Finally, the review identifies future directions, including scaling microfluidic techniques, expanding compatibility with hydrophilic compounds, and integrating machine learning to further enhance the development of nanoprecipitation.},
}

@article {pmid40138794,
year = {2025},
author = {Zhang, L and Wang, K and Zhang, X and Liu, S and Jing, Z and Lu, J and Cui, X and Liu, Z},
title = {Research on the aerodynamic performance and bionic application of dragonfly wing corrugation.},
journal = {Bioinspiration & biomimetics},
volume = {},
number = {},
pages = {},
doi = {10.1088/1748-3190/adc5bc},
pmid = {40138794},
issn = {1748-3190},
abstract = {To investigate the aerodynamic performance of dragonfly wing corrugations under gliding conditions, a new method of corrugation deformation is proposed. Firstly, the coordinate transformation functions that describe the amplitude and camber deformation of the corrugation and numerical simulation model are established. Then the effects of the corrugation structural parameters on airfoil performance are investigated by orthogonal experiment. Subsequently, the optimal structural parameters are selected sequentially, and the mechanism of the corrugation producing a high lift-to-drag ratio is analyzed. The results show that the optimized corrugation parameters are: corrugation profile as profile 5, amplitude coefficient λ = 0.8, vertex x-coordinate a = 0.9c, vertex y-coordinate b = 0.04c. The optimal airfoil achieves the highest lift-to-drag ratio of 5.090, which is increased by 42.82% compared with the flat airfoil. The pressure surface corrugation can increase the pressure difference between the upper and lower surfaces, which is the main reason for the high lift-to-drag ratio. Finally, the bionic airfoils are built by arranging the corrugation on the FFA-W3-211 airfoil, which prove that the dragonfly corrugation with a low Reynolds number is also applicable to the wind turbine airfoil with a high Reynolds number, thereby increasing the lift-to-drag ratio of the prototype airfoil by 1.22%. .},
}

@article {pmid40121369,
year = {2025},
author = {Xia, T and Wei, N and Shi, L},
title = {Large eddy simulation on the wake characteristics of linearly stratified flow past a sphere.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {9970},
doi = {10.1038/s41598-025-94870-w},
pmid = {40121369},
issn = {2045-2322},
support = {12172227//National Natural Science Foundation of China/ ; },
abstract = {In this study, Large Eddy Simulation (LES) has been employed to examine the influence of the Froude number (Fr) on the linearly stratified wake and internal waves behind a sphere at a subcritical Reynolds number of Re = 3700. Six distinct sets of models with varying Fr (Fr = 0.05, 0.25, 0.5, 1, 2, ∞) have been chosen to establish density linear stratification through the use of a User Defined Function (UDF). The analysis focuses on the impact of stratification on wake characteristics, velocity distribution, and the structure of internal waves within stratified flow. It is evident that density stratification plays a pivotal role in shaping wake structure. Notably, in stratified flows, wakes exhibit unique characteristics including the generation of internal waves, suppression of vertical velocity, and the emergence of oscillating wake patterns. The study reveals that a decrease in the Froude number leads to heightened vertical suppression of the wake and increased anisotropy of the velocity distribution. Furthermore, as the Froude number ascends from 0.05 to 2, the wake undergoes a transition from quasi-two-dimensional vortex shedding to three-dimensional turbulence.},
}

@article {pmid40117956,
year = {2025},
author = {Zhu, K and Huang, Y and Yang, L and Xuan, M and Zhou, T and He, Q},
title = {Motion control of chemically powered colloidal motors.},
journal = {Advances in colloid and interface science},
volume = {341},
number = {},
pages = {103475},
doi = {10.1016/j.cis.2025.103475},
pmid = {40117956},
issn = {1873-3727},
abstract = {Chemically powered colloidal motors can convert chemical energy into directional mechanical movement, making them promising for applications such as targeted drug delivery, environmental decontamination, and precision disease treatment. However, their self-propulsion is constantly disrupted by random Brownian motion, making precise control under low Reynolds number conditions highly challenging. This review provides a brief overview of the three main propulsion mechanisms of chemically powered colloidal motors. It also summarizes recent advances in motion control, including speed regulation and trajectory navigation. Finally, we discuss future directions for achieving more precise motion control. We hope this review will inspire further research on developing more effective and practical control strategies for colloidal motors.},
}

@article {pmid40117304,
year = {2025},
author = {Ogawa, T and Koyama, S and Omori, T and Kikuchi, K and de Maleprade, H and Goldstein, RE and Ishikawa, T},
title = {The architecture of sponge choanocyte chambers is well adapted to mechanical pumping functions.},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {122},
number = {12},
pages = {e2421296122},
doi = {10.1073/pnas.2421296122},
pmid = {40117304},
issn = {1091-6490},
support = {JPMJSP2114//MEXT | Japan Science and Technology Agency (JST)/ ; JP24KJ0400//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; JPMJPR2142//MEXT | JST | Precursory Research for Embryonic Science and Technology (PRESTO)/ ; 21H05303//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; 21H05306//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; 22H01394//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; 21H04999//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; 21H05308//MEXT | Japan Society for the Promotion of Science (JSPS)/ ; },
mesh = {Animals ; *Porifera/physiology ; *Flagella/physiology ; Models, Biological ; },
abstract = {Sponges, the basalmost members of the animal kingdom, exhibit a range of complex architectures in which microfluidic channels connect multitudes of spherical chambers lined with choanocytes, flagellated filter-feeding cells. Choanocyte chambers can possess scores or even hundreds of such cells, which drive complex flows entering through porous walls and exiting into the sponge channels. One of the mysteries of the choanocyte chamber is its spherical shape, as it seems inappropriate for inducing directional transport since many choanocyte flagella beat in opposition to such a flow. Here, we combine direct imaging of choanocyte chambers in living sponges with computational studies of many-flagella models to understand the connection between chamber architecture and directional flow. We find that those flagella that beat against the flow play a key role in raising the pressure inside the choanocyte chamber, with the result that the flow rate and mechanical pumping efficiency reach a maximum at a small outlet opening angle. Comparison between experimental observations and the results of numerical simulations reveal that the chamber diameter, flagellar wave number, and the outlet opening angle of the freshwater sponge Ephydatia muelleri, as well as several other species, are related in a manner that maximizes the mechanical pumping functions. These results indicate the subtle balances at play during morphogenesis of choanocyte chambers, and give insights into the physiology and body design of sponges.},
}

Animals
*Porifera/physiology
*Flagella/physiology
Models, Biological

@article {pmid40108425,
year = {2025},
author = {Fu, J and Du, M and Jing, J and Liu, H and Sun, J and Chen, W and Chen, Y},
title = {Prediction of pressure drop in heavy oil water ring based on modified two fluid model.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {9557},
pmid = {40108425},
issn = {2045-2322},
support = {52106208//National Natural Science Foundation of China/ ; 2023NSFSC0924//Natural Science Foundation of Sichuan Province/ ; },
abstract = {Accurate prediction of pressure drop of the heavy oil-water ring flow in pipeline is of great significance for establishing an optimal drag reduction model and ensuring safe production. The effects of different factors on the flow pattern and pressure drop of heavy oil-water annular two-phase flow were systematically analyzed, and a standard two-fluid pressure drop prediction model for annular flow was established. By modifying the shear stress equation of oil-water interface and introducing the wave-flow theory to modify the shear stress equation of water wall, a pressure drop prediction model for the generalized concentric water ring was obtained to calculate the periodic fluctuations of oil phase. Furthermore, by introducing the comprehensive Reynolds number expression of eccentric water ring, the pressure drop prediction model for the generalized eccentric water ring was obtained to calculate the periodic fluctuations of oil phase. The results show that the pressure drop prediction accuracy of the concentric water ring for ultra-heavy oil is improved by 80% by using the modified pressure drop prediction model. The comprehensive Reynolds number expression of eccentric water ring can effectively reflect the influence of eccentric effect on shear stress of water wall and the calculation error is less than 20% by predicting the pressure drop of the generalized eccentric water ring with different density differences.},
}

@article {pmid40102431,
year = {2025},
author = {Gomaa, A and Mhrous, Y and Abdelmagied, MM},
title = {Investigation of the hydraulic and thermal characteristics of a double concentric tubes with an inner twisted spiral tube.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {9301},
pmid = {40102431},
issn = {2045-2322},
abstract = {The characteristics of heat transfer and fluid flow of twisted spiral tubes with different pitches and depths have been investigated experimentally with respect to a conventional tube (smooth tube) as a particular reference. The effects of the twisted spiral pitch ratios, S/Dhy, depth ratios, H/Dhy, Reynolds number and flow arrangement on the thermal performance of a twisted spiral tube heat exchanger are investigated. Three twisted spiral tubes with different pitches, S, of 3.9, 5.2 and 8.2 mm corresponding to twisted spiral pitch ratios, S/Dhy, of 0.278, 0.372 and 0.586; besides three twisted spiral tubes at different depths, H, of 0.6, 0.95, and 1.15 mm corresponding to twisted spiral height ratio, H/Dhy, of 0.043, 0.068 and 0.082 are experimentally examined in this study. The Reynolds number, Re, ranges in both inner tube side and annular side are 5000-50,000 and 1400-10,400, respectively. The results revealed that the twisted spiral pitch ratios S/Dhy of the 0.278achieved an enhancement of Nu by 38% compare to the smooth tube with a corresponding increase of 33.2% in the f. Also, the twisted spiral depths ratios, H/Dhy, of 0.082 achieved higher Nu by 44.9%, compared to the smooth tube with a corresponding increase of 36.4% in the f. The thermal performance criteria reached 1.93 and 2.03 at S/Dhy of 0.278 and H/Dhy of 0.082, respectively. New correlations to expect Nuc and fc were predicted.},
}

@article {pmid40085914,
year = {2025},
author = {Kiran, KV and Kumar, K and Gupta, A and Pandit, R and Ray, SS},
title = {Onset of Intermittency and Multiscaling in Active Turbulence.},
journal = {Physical review letters},
volume = {134},
number = {8},
pages = {088302},
doi = {10.1103/PhysRevLett.134.088302},
pmid = {40085914},
issn = {1079-7114},
abstract = {Recent results suggest that highly active, chaotic, nonequilibrium states of living fluids might share much in common with high Reynolds number, inertial turbulence. We now show, by using a hydrodynamical model, the onset of intermittency and the consequent multiscaling of Eulerian and Lagrangian structure functions as a function of the bacterial activity. Our results bridge the worlds of low and high Reynolds number flows as well as open up intriguing possibilities of what makes flows intermittent.},
}

@article {pmid40077274,
year = {2025},
author = {Weng, C and Wang, Z and Luo, X and Li, H},
title = {Numerical Analysis of Steady-State Multi-Field Coupling in Electro-Fused Magnesia Furnace.},
journal = {Materials (Basel, Switzerland)},
volume = {18},
number = {5},
pages = {},
doi = {10.3390/ma18051049},
pmid = {40077274},
issn = {1996-1944},
support = {No. 2023-GX-102//Special Project for Transformation of Scientific and Technological Achievements of Qinghai Province/ ; 2018YFC1903805//the National Key Research and Development Program of China/ ; 2022YFC2904305//the National Key Research and Development Program of China/ ; 51604059//National Natural Science Foundation of China/ ; },
abstract = {The internal conditions of the high-temperature molten pool in an electro-fused magnesia furnace (EFMF) are difficult to measure, and the temperature distribution-energy conservation relationship in the EFMF cannot be effectively evaluated. Assuming that the feeding speed is constant, the heat absorbed by the newly added raw materials is equal to the rated power minus the heating power required to maintain thermal balance. Therefore, the EFMF can be approximately described by a steady-state model. In order to analyze the state of the molten pool of EFMF at different smelting stages, this study first constructed a three-dimensional steady-state multi-physics field numerical simulation model. The calculations show that the equivalent resistance of the molten pool varies approximately between 1 mΩ and 0.4 mΩ. Furthermore, the equivalent reactance produced by the whole conductive circuit is almost of the same order as the resistance. The Reynolds number of the convection inside the molten pool exceeds 105, which means that the flow inside the molten pool is forced convection dominated by the Lorentz force. Moreover, the turbulence makes the temperature uniformity of the molten pool (the temperature gradient near the solid-liquid interface is approximately within 300 K/m) far greater than that of the unmelted raw materials with very low thermal conductivity (the average temperature gradient reaches over 1000 K/m); the respective proportions of arc power and Joule heating power can be predicted by the model. When the molten pool size is small, the proportion of Joule heating power is high, reaching about 20% of the rated power (3700 kVA); as the molten pool size increases, the convection effect is relatively weakened, and the proportion of Joule heating power also decreases accordingly, only 5% to 10%; the model prediction and experimental estimation results are in good agreement, which makes it feasible to conduct a quantitative analysis of the power distribution in different smelting stages.},
}

@article {pmid40051847,
year = {2025},
author = {Fardin, MM and Hossain, MS and Hasan, MN},
title = {CFD based neural network model framework for mixed convection in a lid-driven cavity with conductive cylinder.},
journal = {Heliyon},
volume = {11},
number = {4},
pages = {e42637},
pmid = {40051847},
issn = {2405-8440},
abstract = {The current study investigates the application of an Artificial Neural Network (ANN) model to analyze and predict mixed convection heat transfer within a 2-dimensional square cavity with a conductive cylinder at the centre. The top lid of the cavity is maintained at a constant cold temperature and slides with a constant linear velocity, while the bottom wall is heated to maintain a constant temperature. The governing equations are discretized using Galerkin Weighted Residual Method and numerically solved using Gauss Quadrature procedure. The ANN model is trained using the data derived from CFD simulations and used to predict the heat transfer performance quantitatively and qualitatively. The setup is investigated for a wide range of Richardson numbers (0.1≤ Ri ≤ 10.0), Reynolds numbers (50 ≤ Re ≤ 250) and cylinder diameters (0.1≤ D/L ≤ 0.8). Heat transfer performance is evaluated from the average Nusselt number along the heated bottom wall. Correlations are established showing dependency of Nusselt number on Ri, Re and D/L. Velocity and thermal fields are expressed by streamlines and isothermal contours. The study shows that higher Richardson and Reynolds numbers lead to an enhancement in the overall heat transfer. But for larger cylinder diameters, heat transfer is mostly dependent on Reynolds number. It is also revealed that substantial improvements in computational efficiency are achieved by the ANN model as it has reduced 82 % of computation time and 83 % of storage requirements to predict the results by maintaining mean absolute error below 0.1 %. The study provides an insight that ANN modelling could open a new dimension to the heat transfer research field and significantly reduce the requirement of time and resources to solve complex problems.},
}

@article {pmid40046270,
year = {2025},
author = {Muhamad Pauzi, A and Iacovides, H and Cioncolini, A and Li, H and Nabawy, MRA},
title = {Application of URANS Simulation and Experimental Validation of Axial Flow-Induced Vibrations on a Blunt-End Cantilever Rod for Nuclear Applications.},
journal = {Arabian journal for science and engineering},
volume = {50},
number = {5},
pages = {3435-3455},
pmid = {40046270},
issn = {2193-567X},
abstract = {Fretting wear caused by flow-induced vibration (FIV) is a leading cause of fuel failure in light water nuclear reactors. This study describes a numerical methodology, validated with dedicated experiments, for predicting flow-induced vibrations in cantilever rods exposed to axial water flow, a paradigmatic configuration informative for fuel rods in water-cooled nuclear reactor cores. Utilising strong two-way fluid-structure interaction (FSI) simulations with an efficient computational approach, the study focuses on two key aspects of self-excited FIV: the dominant vibration frequency and the amplitude of the vibration. Correctly reproducing the former depends on optimising the solid domain and FSI coupling, while the latter hinges on the fluid solver's ability to accurately replicate unsteady flow behaviour, especially in areas of flow separation. Two unsteady Reynolds averaged Navier-Stokes turbulence models, both being high-Reynolds number versions, and several discretisation schemes for the convection transport are evaluated for their capacity to reproduce the correct unsteady flow behaviour. When the axial flow is directed from the free end to the fixed end of the rod, both the Eddy viscosity model k- ω SST and the Reynolds stress model by Launder, Reece, and Rodi reliably predicted the frequency and amplitude of vibrations for a Reynolds number range between 16.4k and 61.7k. When the flow direction is reversed, while vibration frequencies were accurately modelled, replicating precise unsteady flow behaviour proved more challenging. The study underscores the importance of properly resolving the flow in areas of flow separation to achieve accurate simulation of unsteady flow behaviour.},
}

@article {pmid40034269,
year = {2025},
author = {Jahin, AS and Samin, JH and Chhoa, MF and Faisal, F and Nokib, MHI and Rabby, MII},
title = {Computational study of thermofluidic characteristics of Al2O3-Cu hybrid nanofluids in backward facing step channel with varying step angles.},
journal = {Heliyon},
volume = {11},
number = {4},
pages = {e42638},
pmid = {40034269},
issn = {2405-8440},
abstract = {Backward-Facing Step (BFS) channels are frequently utilized in technical implementation due to their ability to model intricate fluid flow patterns, such as recirculation zones, which have significant impacts on thermal exchange rates. This research investigates the thermal and heating efficiency of Al2O3-Cu hybrid nanofluids in a BFS channel, focusing on the effects of varying step angles and Reynolds numbers (Re) on thermal efficiency. ANSYS Fluent (2021 R2) was used to analyze Al2O3-Cu nanofluids across Reynolds numbers (500-800), step angles (70°, 75°, 80°, and 85°), and particle volumes (1%-4%) applying the finite volume method. The results demonstrate that as the Reynolds number increases, the Nusselt number rises by an average of 18.505 %. In contrast, varying the step angle results in an average increase of 4.94 %. It is also observed that an increase in volume fraction of nanoparticles enhances the Nusselt number due to the superior thermal conductivity of the Al2O3-Cu nanofluid. Additionally, a positive correlation between step angle, skin friction coefficient, and pressure drop was observed.},
}

@article {pmid40019202,
year = {2025},
author = {Lopez, M and Benchikh Le Hocine, AE and Kone, TC and Dupont, T and Panneton, R},
title = {Inertial effects on single-perforation plates resistivity at high flow rates: Computational fluid dynamics and experimental studies.},
journal = {The Journal of the Acoustical Society of America},
volume = {157},
number = {2},
pages = {1512-1522},
doi = {10.1121/10.0035642},
pmid = {40019202},
issn = {1520-8524},
abstract = {This article is focused on the viscous and inertial effects on airflow resistivity of periodic arrays of single-perforation plates spaced by thin air cavities. Analyzing this effect would provide better insight into losses within the material, including additional losses due to increasing sound excitation levels. In this way, the material pressure drop is predicted by computational fluid dynamics function (CFD) of the flow rate for corresponding pore Reynolds numbers between 0.3 and 1500. The static airflow resistivity coefficient is determined by the linear part of the pressure drop (viscous effect) and the Forchheimer coefficient from the nonlinear part of the pressure drop (inertial effect). Both coefficients are determined on the entirety of the material (globally) and at the plate levels (locally). Good agreement is observed between CFD predictions and experimental measurements on the whole range of studied Reynolds numbers. By locally investigating the pressure drops, the observations show that the viscous effects are constant through the material. With increasing pore Reynolds number, inertial effects of the first plate dominate over those of the other plates. The consideration of the local inertial effect will be a key component in the acoustic modeling of this type of material under high sound excitation levels.},
}

@article {pmid40011611,
year = {2025},
author = {Gomaa, A and Gamal, Y and Abdelmagied, MM},
title = {Enhancement of thermofluid characteristics via a triple-helical tube heat exchanger.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {6978},
pmid = {40011611},
issn = {2045-2322},
abstract = {An investigation of the thermal and hydraulic performance of a novel triple-helical tube heat exchanger, the THTHE, is presented. The novel design is a modified design of a DHTHE created by adding a third tube to a DHTHE tube. The third passage is expected to enhance the thermal performance of the DHTHE as a result of an increase in the temperature gradient between the hot and cold fluids. The effects of the coil radius, inner annulus spacing, water inlet temperature, direction of flow arrangement, and Dean number were explored. Five test samples with different coil radii of 150 mm, 125 mm, and 90 mm and different inner annulus spacings of 6.2 mm, 9 mm, and 12 mm were examined. The test samples were designed, fabricated, and tested to demonstrate the influence of design parameters on the thermal and hydraulic performance of the triple-helical tube heat exchanger. The experimental runs were conducted on the hot water side with the water inlet temperature Th,i ranging from 50:80 °C. Moreover, at Dean number 400 ≤ Deh ≤ 5500, corresponding to Reynolds number 2700 ≤ Reh ≤ 31,000. Compared with the double-helical tube heat exchanger, the THTHE resulted in a higher Nusselt number by 146.1% and 109.3% for both the counterflow and parallel-flow arrangements, respectively. Furthermore, lowering the hot water source temperature from 80 to 50 °C results in a 60.6% increase in the Nusselt number of 60.6%, with no increase in the pumping power. Additionally, with a decreasing coil radius from 150 to 90 mm and inner annulus spacing from 12 to 6.2 mm, a significant increase in Nu occurs by 58.2% and 130.4%, respectively. A general correlation was presented for predicting Nu, f, and ε.},
}

@article {pmid40009542,
year = {2025},
author = {Zhang, Y and Wang, X and Han, J and Xiao, J and Yong, Y and Yu, C and Yue, N and Sun, J and He, K and Hao, W and Zhang, T and Wang, B and Wang, D and Yang, X},
title = {Dynamic simulations of feeding and respiration of the early Cambrian periderm-bearing cnidarian polyps.},
journal = {eLife},
volume = {12},
number = {},
pages = {},
doi = {10.7554/eLife.90211},
pmid = {40009542},
issn = {2050-084X},
support = {42372012//Natural Science Foundation of China/ ; XDB26000000//Chinese Academy of Sciences/ ; D17013//Ministry of Education of China/ ; BJ11060//Northwest University/ ; 2023YFF0803601//National Key Research and Development Program of China/ ; Z6122059//Linyi University/ ; 41720104002//Natural Science Foundation of China/ ; 41911530236//Natural Science Foundation of China/ ; },
mesh = {Animals ; *Feeding Behavior/physiology ; *Fossils ; *Respiration ; *Cnidaria/physiology/anatomy & histology ; China ; Computer Simulation ; Hydrodynamics ; },
abstract = {Although fossil evidence suggests the existence of an early muscular system in the ancient cnidarian jellyfish from the early Cambrian Kuanchuanpu biota (ca. 535 Ma), south China, the mechanisms underlying the feeding and respiration of the early jellyfish are conjectural. Recently, the polyp inside the periderm of olivooids was demonstrated to be a calyx-like structure, most likely bearing short tentacles and bundles of coronal muscles at the edge of the calyx, thus presumably contributing to feeding and respiration. Here, we simulate the contraction and expansion of the microscopic periderm-bearing olivooid Quadrapyrgites via the fluid-structure interaction computational fluid dynamics (CFD) method to investigate their feeding and respiratory activities. The simulations show that the rate of water inhalation by the polyp subumbrella is positively correlated with the rate of contraction and expansion of the coronal muscles, consistent with the previous feeding and respiration hypothesis. The dynamic simulations also show that the frequent inhalation/exhalation of water through the periderm polyp expansion/contraction conducted by the muscular system of Quadrapyrgites most likely represents the ancestral feeding and respiration patterns of Cambrian sedentary medusozoans that predated the rhythmic jet-propelled swimming of the modern jellyfish. Most importantly for these Cambrian microscopic sedentary medusozoans, the increase of body size and stronger capacity of muscle contraction may have been indispensable in the stepwise evolution of active feeding and subsequent swimming in a higher flow (or higher Reynolds number) environment.},
}

Animals
*Feeding Behavior/physiology
*Fossils
*Respiration
*Cnidaria/physiology/anatomy & histology
China
Computer Simulation
Hydrodynamics

@article {pmid40007569,
year = {2025},
author = {Mohan, A and Ramanan, SR},
title = {Surface imprinted microhelical magnetic polymer nanocomposite fibers for targeted lysozyme separation.},
journal = {Nanoscale advances},
volume = {},
number = {},
pages = {},
pmid = {40007569},
issn = {2516-0230},
abstract = {Magnetic microhelical structures have recently drawn attention as microswimmers capable of mimicking bacterial propulsion in the low Reynolds number regime. Such structures can be used in microfluidic bioseparation or targeted delivery and their interaction with proteins is extremely important. In this study we fabricated silica coated magnetic microhelices resembling artificial bacterial flagella like structures via electrospinning magnetite nanoparticle incorporated polystyrene nanocomposite solution followed by silica sol coating. Two model proteins, Lysozyme (Lyz) and Bovine Serum Albumin (BSA), were used for protein imprinting along with a polydopamine layer on the magnetic microhelical substrates. The adsorption mechanism of lysozyme on the molecularly imprinted support system was analyzed using adsorption model fitting (Langmuir, Freundlich and Temkin). Adsorption capacity, selective binding and imprinting factor values were calculated for both imprinted (Lyz and BSA) and non-imprinted samples. A significantly higher adsorption capacity was obtained compared to previously reported studies.},
}

@article {pmid40001473,
year = {2025},
author = {Zhuang, XY and Lo, CJ},
title = {Decoding Bacterial Motility: From Swimming States to Patterns and Chemotactic Strategies.},
journal = {Biomolecules},
volume = {15},
number = {2},
pages = {},
doi = {10.3390/biom15020170},
pmid = {40001473},
issn = {2218-273X},
support = {NSTC-109-2628-M-008-01-MY4//NSTC/ ; NSTC 113-2112-M-001-059-MY3.//NSTC/ ; },
mesh = {*Chemotaxis ; *Flagella/physiology ; *Bacteria/metabolism ; Bacterial Physiological Phenomena ; Movement ; },
abstract = {The bacterial flagellum serves as a crucial propulsion apparatus for motility and chemotaxis. Bacteria employ complex swimming patterns to perform essential biological tasks. These patterns involve transitions between distinct swimming states, driven by flagellar motor rotation, filament polymorphism, and variations in flagellar arrangement and configuration. Over the past two decades, advancements in fluorescence staining technology applied to bacterial flagella have led to the discovery of diverse bacterial movement states and intricate swimming patterns. This review provides a comprehensive overview of nano-filament observation methodologies, swimming states, swimming patterns, and the physical mechanisms underlying chemotaxis. These novel insights and ongoing research have the potential to inspire the design of innovative active devices tailored for operation in low-Reynolds-number environments.},
}

*Chemotaxis
*Flagella/physiology
*Bacteria/metabolism
Bacterial Physiological Phenomena
Movement

@article {pmid39972743,
year = {2025},
author = {Verma, S and Seshasayanan, K},
title = {Effects of radial conductivity variation on the Ponomarenko dynamo.},
journal = {Physical review. E},
volume = {111},
number = {1-2},
pages = {015207},
doi = {10.1103/PhysRevE.111.015207},
pmid = {39972743},
issn = {2470-0053},
abstract = {We study the effects of conductivity variation on the Ponomarenko dynamo. Taking monotonically increasing, decreasing and sinusoidally varying radial profiles, we study the kinematic dynamo problem. The threshold of the dynamo, given by the critical magnetic Reynolds number Rm_{c},
is found to strongly depend on the form of conductivity variation near the discontinuity of the velocity field where the shear is dominant. For monotonically varying profiles in the limit of sharp variation, this threshold maps to the problem of the dynamo with a jump in conductivity, while for the sinusoidal profile with large variations or wave numbers, the threshold increases due to effective diffusivity arising from the rapid changes in conductivity. Far from the threshold, it is found that the growth rate depends only on the local gradient of the conductivity near the discontinuity, with the opposite sign of shear and conductivity gradient leading to a larger growth rate, thereby aiding the dynamo instability in regenerating B_{ϕ}
from B_{r}.
We calculate the expression for the growth rate in the limit of large Rm(≫1) and find that the conductivity variation leads to a modification proportional to the local gradient of conductivity times Rm^{-1/2}.
This correction is found to depend only on the local gradient of the conductivity at the discontinuity. Similar dependencies are found for realistic, smooth velocity profiles and for different magnetic boundary conditions.},
}

@article {pmid39958364,
year = {2025},
author = {Bose, C and Bruce, C and Viola, IM},
title = {Porous plates at incidence.},
journal = {Theoretical and computational fluid dynamics},
volume = {39},
number = {2},
pages = {19},
pmid = {39958364},
issn = {0935-4964},
abstract = {This paper investigates the effect of permeability on two-dimensional rectangular plates at incidences. The flow topology is investigated for Reynolds number (Re) values between 30 and 90, and the forces on the plate are discussed for R e = 30 , where the wake is found to be steady for any value of the Darcy number (Da) and the flow incidence (α). At R e = 30 , for a plate normal to the stream and vanishing Da, the wake shows a vortex dipole with a stagnation point on the plate surface. With increasing Da, the separation between the vortex dipole and the plate increases; the vortex dipole shortens and is eventually annihilated at a critical Da. For any value of Da below the critical one, the vortex dipole disappears with decreasing α . However, at low Da, the two saddle-node pairs merge at the same α , annihilating the dipole; while at high Da, they merge at different α , resulting in a single recirculating region for intermediate incidences. The magnitudes of lift, drag, and torque decrease with Da. Nevertheless, there exists a range of Da and α , where the magnitude of the plate-wise force component increases with Da, driven by the shear on the plate's pressure side. Finally, the analysis of the fluid impulse suggests that the lift and drag reduction with Da are associated with the weakening of the leading and trailing edge shear layer, respectively. The present findings will be directly beneficial in understanding the role of permeability on small permeable bodies.},
}

@article {pmid39953100,
year = {2025},
author = {Zhang, T and Li, F and Fan, J},
title = {Impact of corner optimization measures on the interference effects between two square section buildings.},
journal = {Scientific reports},
volume = {15},
number = {1},
pages = {5558},
pmid = {39953100},
issn = {2045-2322},
support = {//National Natural Science Foundation of China/ ; },
abstract = {Wind-induced interference effects occur between high-rise twin buildings. To elucidate the impact of aerodynamic optimization measures on the interference effects between high-rise buildings, large eddy simulations (LES) were conducted to analyze the wind load characteristics of buildings with varying spacing. The simulation results were compared with experimental data and previous studies to validate the method's accuracy. To investigate the influence of various aerodynamic corner optimizations on interference effects between high-rise buildings, LES was employed to simulate wind load characteristics. Simulation results were compared with experimental data and previous studies to ensure the method's accuracy. Three corner treatments-chamfered, rounded, and recessed-were applied to the model, with a corner modification rate of 10%. Under wind field conditions corresponding to a Reynolds number (Re) of 22,000, 10 simulated schemes with spacing ratios (B/L) ranging from 1.2 to 8 were considered, where B represents the center-to-center distance between two square cylinders, and L denotes the side length of each square cylinder. The aerodynamic coefficients, flow field mechanisms, and vorticity of the two side-by-side square cylinders under three corner treatments were compared. Additionally, peak factors were calculated based on predefined measurement points to further assess differences in interference factors. Using the Lorentz function, the peak fitting curve of the wind pressure probability density was compared with the Gaussian fitting curve. The analysis indicates that the wind pressure shielding effect is most pronounced for the rounded corner square cylinder, while the amplification effect is strongest for the chamfered corner square cylinder. At critical spacing, the adjacent facades of the recessed corner square cylinders exhibited a bimodal distribution in wind pressure probability density.},
}