Physical Review Fluids

Author(s): Nataly Maroundik, Dotan Ilssar, and Evgeniy Boyko

Diffusioosmotic flow, driven by solute concentration gradients, is a widely used method for fluid manipulation in microfluidic devices, often fabricated from soft materials such as PDMS. We show that such soft diffusioosmotic flow systems may exhibit fluid-structure instability. To provide insight into the underlying instability mechanism, we develop a theoretical model describing the interaction between diffusioosmotic flow and an elastic substrate. We find that above a certain concentration gradient threshold, negative pressures induced by diffusioosmotic flow cause the collapse of the elastic top substrate onto the bottom surface.

[Phys. Rev. Fluids 10, 104203] Published Tue Oct 14, 2025

Author(s): Imran Hayat and George Ilhwan Park

Three-dimensional turbulent boundary layers subject to pressure gradients and undergoing separation remain a key challenge for wall modeling. Using DNS datasets of swept and unswept separation bubbles, this study employs the Renard–Deck skin-friction decomposition to isolate and analyze nonequilibrium contributions critical to near-wall modeling. Wall-modeled LES demonstrates that only wall models capturing the spatial growth term accurately reproduce the true energy balance in nonequilibrium zones. The analysis highlights when and why nonequilibrium effects must be incorporated, providing physics-based guidance for improving wall model predictions in practical flows.

[Phys. Rev. Fluids 10, 104602] Published Tue Oct 14, 2025

Author(s): G. D'Avino, M. M. Villone, M. De Corato, S. Villa, M. Nobili, and D. Larobina

The mobility of elongated colloidal particles near fluid interfaces is crucial in fields ranging from biofilm formation to thin-film technologies. This study numerically investigates the resistance matrix of a prolate spheroid close to a two-dimensional incompressible liquid–gas interface, revealing that surface incompressibility mimics slip conditions for parallel motion and no-slip for orthogonal motion. The results align with recent experimental data and highlight the role of interface hydrodynamics in colloidal transport.

[Phys. Rev. Fluids 10, 104002] Published Fri Oct 10, 2025

Author(s): Ethan Coleman and Ankur Gupta

Electrolytic diffusiophoresis refers to the movement of charged particles in electrolytes. This motion typically proceeds either up or down an electrolyte concentration gradient. However, when multiple electrolyte gradients are present, such as an acid-base reaction, the direction may be reversed, inducing the formation of a focal band. While the results were reported experimentally, an understanding of the phenomena has remained elusive. Here, we computationally show that a pH-dependent zeta-potential is required for focusing to occur. Our model provides an intuitive understanding of the governing physics and a compelling match to prior experimental reports.

[Phys. Rev. Fluids 10, 103701] Published Thu Oct 09, 2025

Author(s): Daniel Papa, Christophe Josserand, and Caroline Cohen

Do ice stalagmites grow purely vertically? Our work shows that depending on the substrate temperature and the water flow rate, ice stalagmites can take a wide variety of shapes and forms. We determined a criterion that distinguish a purely vertical growth to a combined vertical and lateral growth dynamics. We also show that the main driving factor is the heat diffusion at the stalagmite’s tip and that the combined knowledge of both the vertical and lateral growth allows us to determine the asymptotic aspect ratio of the ice stalagmites. Our predictions are compared and validated by experiments and can serve as a model experiment to study related physical phenomena.

[Phys. Rev. Fluids 10, L101602] Published Thu Oct 09, 2025

Author(s): Laura K. Currie and Chris A. Jones

Jupiter’s zonal winds extend down about 3000 km into its interior but the mechanism that determines this depth is currently unknown. Here we explore a mechanism by which the surface zonal flows of giant planets can be gradually attenuated. We show that the combination of a stably stratified surface layer, a zonal flow driven near the surface, and convection in thermal wind balance can lead to zonal jets that extend deep into the interior, consistent with gravity data from observations.

[Phys. Rev. Fluids 10, 103501] Published Tue Oct 07, 2025

Author(s): Romain Noël, Feifei Qin, Linlin Fei, and Jan Carmeliet

We propose an alternative surface tension adjustment approach in the pseudopotential lattice Boltzmann (LB) model, which can be easily and straightforwardly incorporated into different widely used collision operators, such as single relaxation time (SRT or LBGK), multiple relaxation time (MRT) and entropic-MRT (KBC) operators. Benefiting from the proposed surface tension adjustment method, a remarkable tunable surface tension range of 140 times can be achieved. We have also successfully modeled the droplet impact and splashing dynamics on thin liquid films with a Weber number up to 10,500, achieving one order of magnitude higher than LB simulations reported in the literature.

[Phys. Rev. Fluids 10, 104901] Published Tue Oct 07, 2025

Author(s): Guilhem Balvet, Yelva Roustan, and Martin Ferrand

This study presents a consistent framework for high-Reynolds-number, thermally stratified surface boundary layers, linking turbulence models to universal profiles of velocity and temperature. By deriving algebraic solutions for second-order moments and iteratively resolving dissipation, the approach recovers correct stable and unstable asymptotics. Implications for Lagrangian stochastic models are explored, highlighting the need for consistent turbulence closures and wall-boundary treatments in predicting buoyant plume rise and dispersion.

[Phys. Rev. Fluids 10, 103801] Published Mon Oct 06, 2025

Author(s): Joseph J. Webber and Thomas D. Montenegro-Johnson

Self-oscillating gels that swell and deswell due to an oscillating chemical reaction can be used to pump fluid in pulses. This allows us to design a two-sphere microswimmer that can locomote in the Stokes regime from responsive hydrogels, with an external driving force arising from the chemical field. Using a model for the swelling and deswelling of such gels, and the flows that they generate, we compute analytical expressions for the swimming velocity and how it depends on the asymmetry of the gel spheres, and further show that swimmers can ‘surf’ rapidly along chemical waves in a reaction-diffusion system.

[Phys. Rev. Fluids 10, 100501] Published Fri Oct 03, 2025

Author(s): Blaise Delmotte and Florencio Balboa Usabiaga

This Perspective highlights the rigid multiblob framework, a numerical method for modeling suspensions of complex-shaped particles influenced by hydrodynamics, thermal fluctuations, activity, and other interactions. This review illustrates the effectiveness and versatility of the method in tackling a wide range of physical problems in fluid mechanics, soft and active matter, biophysics, and colloidal science.

[Phys. Rev. Fluids 10, 100701] Published Fri Oct 03, 2025

Author(s): Rupayan Jana and Shubhadeep Mandal

In this work, we semianalytically investigate the influence of an imposed spatially linearly varying viscosity field on near wall motion of a model microswimmer (squirmer). We explore its associated phase portraits and swimming trajectories for different swimming gaits and compare them with their constant viscosity analogs. The results indicate that even simplistic ambient viscosity gradient has substantial role on near-wall squirmer motility, which provides valuable insights for understanding and controlling microswimmer motion in relatively complex biological and microfluidic systems.

[Phys. Rev. Fluids 10, 104201] Published Fri Oct 03, 2025

Author(s): Cong Han and Arindam Banerjee

Tidal turbines deployed at tidal energy sites suffer high-turbulence flows, posing challenges for the estimation of their survivability and energy production. Our work implements an active grid to generate a homogeneous, high-turbulence flow replicating the flow characteristics at those sites in a water tunnel. Important terms in the Reynolds-averaged Navier–Stokes equations are quantified based on the measured wake field data for a comprehensive wake recovery analysis. The results further demonstrate that the tip vortices become extremely unstable under turbulence within one diameter downstream, reshaping the distribution of turbulence kinetic energy production and Reynolds shear stresses.

[Phys. Rev. Fluids 10, 104601] Published Fri Oct 03, 2025

Author(s): Joseph J. Kilbride, F. Fouzia Ouali, and David J. Fairhurst

If you have ever breathed on a window, you will have seen fog condense, which quickly evaporates from its edge to its center. The fog contains millions of individual micron-sized droplets, which when confined evaporate much slower and can be studied under a microscope. Interestingly, despite the fog evaporating overall, in the center of the fog, individual droplets can grow whilst small droplets shrink and Ostwald ripening is observed. In this paper, we track thousands of individual droplets and compare to classic Ostwald ripening theory, finding good agreement. We then show that a mean field model can predict the dynamics of the hundreds of individual droplets imaged.

[Phys. Rev. Fluids 10, L101601] Published Fri Oct 03, 2025

Author(s): Rotem Soffer, Eliezer Kit, and Yaron Toledo

The potential approach has been considered a reliable standard in computing wave directional spectra from instrumental measurements. However, by definition, it neglects ambient shearing currents. We present a proof that this oversight can lead to significant deviations of first-order in wave directional spectra estimates (height and direction), and propose a methodology based on rotational theory. The study demonstrates that shearing currents must not be neglected in wave data processing. A comparison of the rotational and potential approaches using the Acoustic Doppler Current Profiler (ADCP) dataset reveals notable and consistent differences in wave parameter estimation for in situ data.

[Phys. Rev. Fluids 10, 104801] Published Thu Oct 02, 2025

Author(s): Zachary G. Lipel, Yannick A. D. Omar, and Dimitrios Fraggedakis

The finite thickness of cell membranes is an often-overlooked detail in continuum models that can change their physics in fundamental ways. We show that when the bilayer bends, shear flows arise at its two surfaces, producing flow reversal, pressure inversion, and stagnation points that standard two-dimensional models cannot capture. Our findings highlight a missing element in existing continuum theories: resolving coupling at the membrane’s two surfaces requires accounting for thickness. This refinement predicts new nanoscale dissipation mechanisms and suggests experimental signatures in fluctuation spectra, pointing toward a more unified description of membrane dynamics.

[Phys. Rev. Fluids 10, 103101] Published Wed Oct 01, 2025

Author(s): Pijush Patra, Anubhab Roy, and J. S. Wettlaufer

Rain formation in warm clouds begins with the collision and coalescence of tiny water droplets, influenced by the electric charges they carry and the electric fields within clouds. The collision rate determines how quickly larger droplets form, which ultimately influences precipitation. Understanding the effects of electrostatic forces on droplet collisions is vital for improving cloud microphysics parameterizations and thus applications such as weather forecasting. This study shows that strong electric fields generated during cloud electrification can significantly enhance the collision efficiency of droplets subject to a laminar flow.

[Phys. Rev. Fluids 10, 103601] Published Wed Oct 01, 2025

Author(s): Bin Wu, Yunhua Jiang, and Zhihui Zou

A novel method utilizing an air jet to assist the water exit of a model is proposed. The air jet penetrates the water surface and generates a cavity, enabling the model to move within the jet-induced air environment. This ventilated cavity moves synchronously with the model, showing significant potential to mitigate asymmetric impact loads caused by cavity collapse. This study enhances the understanding of artificial cavity formation and is expected to address issues such as structural failure and trajectory instability during vehicle water exit, which arise from asymmetric impact loads caused by the cavity collapse.

[Phys. Rev. Fluids 10, 104001] Published Wed Oct 01, 2025

Author(s): Oleksander Krul and Prosenjit Bagchi

In the microcirculation, highly deformable red blood cells flow through vessels of comparable size. Many of these vessels are compliant, but the impact of their deformation on the cell dynamics remains largely unexplored. Motivated by this, a computational study using a three-dimensional fully coupled fluid-structure interaction model is presented on the flow of deformable capsules in a compliant, inflating tube. The tube’s inflation is found to significantly alter the capsules’ transient deformation and velocity. Additionally, interactions between the capsule and tube create flow rate oscillations that are absent in a rigid tube under similar flow conditions.

[Phys. Rev. Fluids 10, 093105] Published Mon Sep 29, 2025

Author(s): Tianyi Chu, Benjamin Wilfong, Timothy Koehler, Ryan M. McMullen, and Spencer H. Bryngelson

Interfacial Rayleigh–Taylor (RT) and Faraday instabilities are usually studied separately, one driven by pressure gradients, the other by parametric resonance. Their coexistence produces a previously unidentified multi-modal instability. Floquet analysis and numerical simulations reveal a bidirectional competition: the Faraday mechanism, amplified by vibration, suppresses RT modes, while residual RT dynamics nonlinearly attenuate Faraday responses. This interaction advances understanding of interfacial mixing under combined forcing.

[Phys. Rev. Fluids 10, 093904] Published Mon Sep 29, 2025

Author(s): Robert Hicks and H. Reed Ogrosky

Thin-film modeling provides a computationally inexpensive way to quantify viscous film transport arising due to gravity and/or shear flow in tubes. Previous work has largely focused on tubes with fixed mean radius; this study quantifies the impact of a time-dependent radius on film transport. Linear stability analysis of this periodically-forced model shows that tube contractions/expansions enhance instability growth relative to a rigid tube. Simulations of the full nonlinear model equation highlight the role of free-surface waves in enhancing transport. Parameter values used here are motivated by the human lung/airway system.

[Phys. Rev. Fluids 10, 094008] Published Mon Sep 29, 2025