Physical Review Fluids

Author(s): R. J. Teed and E. Dormy

Recent numerical experiments of dynamo action relevant to the generation of the geomagnetic field have produced different regime branches identified within bifurcation diagrams. In this work, we identify a variety of dynamo states on the weak-field branch beyond the known dipolar solutions. Some solutions exhibit clear scale separation between small-scale flow and large-scale magnetic field, despite the large ratio of viscosity to magnetic diffusion. Numerical solutions in this regime have not been observed before and they offer a first connection with earlier theoretical work based on mean-field theory.

[Phys. Rev. Fluids 10, 103702] Published Wed Oct 15, 2025

Author(s): Dongqi Li, Zhibing Yang, Renjun Zhang, Amir A. Pahlavan, Ran Hu, and Yi-Feng Chen

Understanding particle-mediated interfacial processes in confined spaces undergoing deformation is important for many natural and industrial processes. Here, we combine laboratory experiments and theoretical analysis to investigate how particle dynamics shapes suspension-air interfacial pattern formation when the suspension is stretched. It is found that even slightly nonuniform particle concentration promotes wavy and finger-like morphologies, while particle perturbations lead to dendritic pattern with strong finger branching.

[Phys. Rev. Fluids 10, 104004] Published Wed Oct 15, 2025

Author(s): Darren Crowdy

The mechanism of surfactant diffusion between two edges of the active face of a Janus swimmer is shown to lead to a translational-rotational coupling leading to swimming in circles. The mechanism is exemplified using a two-dimensional model system amenable to closed-form representation of the swimmer trajectory and the Stokes flow it generates.

[Phys. Rev. Fluids 10, 104101] Published Wed Oct 15, 2025

Author(s): Dario De Marinis, Domenico Careccia, Francesco Ferrara, and Marco Donato de Tullio

This study employs a Lattice Boltzmann-based fluid-structure interaction framework to investigate how channel geometry, particle properties, and flow regimes affect inertial migration and secondary flows in curved microchannels. After validation against benchmark cases, the work reports, for the first time, fully resolved numerical simulations of multiple-particle focusing in realistic serpentine microchannel geometries.

[Phys. Rev. Fluids 10, 104202] Published Wed Oct 15, 2025

Author(s): Jun Hu, Ruiwei Xing, and Baofang Song

This study explores instabilities of an upward mixed convection flow in a vertical heated pipe under a transverse magnetic field through linear global stability analysis and direct numerical simulations. The critical curves in the parameter plane of the Rayleigh number and the Hartmann number are presented for both thermal-buoyant and thermal-shear instabilities, and reveal that under the action of the magnetic field the two plane symmetric spiral modes are broken into two asymmetric branches. Direct numerical simulations are further used to investigate the transition routes from regular laminar flows to more complex nonlinear spatiotemporal structures.

[Phys. Rev. Fluids 10, 103901] Published Tue Oct 14, 2025

Author(s): Megan Delens and Nicolas Vandewalle

Capillary-driven self-assembly at liquid interfaces, often illustrated by the “Cheerios effect,” has been limited to simple configurations. By introducing anisotropic, saddle-shaped particles, we demonstrate how quadrupolar capillary interactions can be encoded to achieve both end-to-end and side-by-side attraction; what we call the “Pringles effect.” Our theoretical model and experiments with 3D-printed objects reveal a versatile route to reprogrammable mesoscale assemblies, bridging capillarity and design for complex self-organization.

[Phys. Rev. Fluids 10, 104003] Published Tue Oct 14, 2025

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