Physical Review Fluids

Author(s): Sourav Kumar Singh, Vishant Tyagi, and Aritra Santra

Dense suspensions of non-Brownian particles encountered in industrial processes like concrete mixing, chocolate refining, and ceramic processing are well known to show abrupt jamming transition under shear flow, yet, the effects of particle size distribution on this transition remain poorly understood. Using Discrete Element Method-based simulations in two dimensions, the authors show that polydisperse suspensions undergo critical rigidity transition preceding shear jamming, with scaling exponents consistent with percolation theory. Remarkably, the order parameter, susceptibility, and the microstructural properties of polydisperse suspensions are found to be identical to those of the statistically equivalent bidisperse systems

[Phys. Rev. Fluids 11, 054307] Published Fri May 22, 2026

Author(s): Itzhak Fouxon, Hojun Lee, and Changhoon Lee

Fluids in nature are usually turbulent and contain small particles, a phenomenon observed in paper production, rain formation, astrophysics, and the oceans, among other places. These particles are more often than not nonspherical, such as fibers in paper. Particle orientation in the flow determines how the flow drags them and, eventually, how the particles distribute in space and orient. We use a symmetry-based simplification, analogous to a classical description of neutrally buoyant spheroids, to introduce a new framework for flows with nonspherical particles, which yields a compact set of evolution equations with fewer degrees of freedom.

[Phys. Rev. Fluids 11, 054903] Published Fri May 22, 2026

Author(s): Pratyush Kumar Mohanty, P. S. D. Surya Phani Tej, Ganesh Subramanian, and V. Shankar

The eigenspectrum of bounded viscoelastic shearing flows comprises a continuous spectrum (CS) whose eigenvalues form continuous curves or line segments in the complex plane, in addition to a discrete spectrum of isolated eigenvalues. While the Oldroyd-B model possesses only two line-segment CS, we show that the more realistic FENE-P model admits up to six distinct CS. Our analytical predictions provide a framework for interpreting numerically computed spectra of viscoelastic shearing flows.

[Phys. Rev. Fluids 11, 053304] Published Thu May 21, 2026

Author(s): Thomas Frisch, Christophe Josserand, and Sergio Rica

Direct numerical simulations and full analytical theory reveal how the geometry of obstacles determines the onset of vortex nucleation in quantum fluids such as Bose–Einstein condensates and related superfluid systems. In particular, the flows around obstacles with sharp corners such as walls and wells display a time-irreversible transition when the velocity exceeds a critical value which is well below the sound speed. This work paves the way for the study of skin friction in superfluid systems.

[Phys. Rev. Fluids 11, 054703] Published Wed May 20, 2026

Author(s): Wietze Herreman, Basile Dhote, and Frédéric Moisy

Bendable thin structures such as floating modular pontoons can be displaced, rotated and deformed by incoming gravity waves. We propose a diffractionless theory to calculate the second order mean yaw moment on slender elastic structures in waves. In the case of non-moored, freely drifting floaters, the mean yaw moment can rotate the structure to a preferential orientation with respect to the angle of incidence. Using our theory, we can predict this preferential orientation and how it varies with floater shape and its bending modulus.

[Phys. Rev. Fluids 11, 054803] Published Wed May 20, 2026

Author(s): Yuzhe Qin, Huaxiong Huang, Zilong Song, and Shixin Xu

Most electrohydrodynamic droplet models assume passive ion transport and field-induced polarization. Here we incorporate chemically powered active interfacial ion transport into a Navier–Stokes – Poisson–Nernst–Planck – Cahn–Hilliard (NS-PNP-CH) phase-field framework using an energy–dissipation–input formulation. The resulting persistent charge asymmetry reorganizes electric fields and stresses, enabling controlled deformation, breakup and recoalescence, as well as droplet separation under shear.

[Phys. Rev. Fluids 11, 053702] Published Tue May 19, 2026

Author(s): Bilal Fareed, Muhammad Nadeem, Atta Ullah, John J. Molina, Ryoichi Yamamoto, Leonardo P. Chamorro, and Adnan Hamid

Sedimentation of nonspherical particles is typically governed by orientation-dependent interactions. We show that cube-shaped particle suspensions recover classical Stokesian scaling laws associated with spheres. This behavior emerges from geometric symmetry, which suppresses anisotropy and promotes isotropic microstructure. The results identify symmetry, not sphericity, as the key determinant of collective sedimentation dynamics.

[Phys. Rev. Fluids 11, 054305] Published Tue May 19, 2026

Author(s): Juan Pimienta and Jean-Luc Aider

We demonstrate for the first time that it is possible to access in real-time (live measurements) two-dimensional instantaneous velocity fields with both high spatial resolution and high sampling frequency. Using a standard Optical Flow algorithm properly optimized, standard 4Mp snapshots can be processed live up to 460 Hz. Moreover, using the proper experimental settings, it also becomes possible to access 1 vector per pixel, leading to very high spatial resolution. Apart from considerable gain in computing time and power consumption, this approach also unlocks new experiments like very low frequency measurements, closed-loop flow control, or rare events detection.

[Phys. Rev. Fluids 11, 054902] Published Tue May 19, 2026

Author(s): Ron Bessler, Tirosh Mekler, Daniel Malka, Nadia Onallah, Oshri Farhana, Rami Fishler, Saurabh Bhardwaj, Kenichiro Koshiyama, Netanel Korin, and Josué Sznitman

Existing studies of charged aerosol deposition have largely focused on isolated upper-airway or local truncated in vitro models, leaving whole-lung scale effects unresolved. Using a physiologically inspired multiscale airway-on-chip spanning conducting to acinar regions, we investigated the electrostatic contributions along with gravity, impaction, and diffusion. Our results show that charge significantly reshapes deposition patterns, enhancing early bronchiolar capture while reducing delivery to the distal acinus.

[Phys. Rev. Fluids 11, 050501] Published Mon May 18, 2026

Author(s): Yu-Hang Xiong, An-Kang Gao, Xi-Yun Lu, and Shaohua Chen

Flexible appendages performing metachronal rowing can efficiently transport fluid, but the role of elasticity in impulsively driven systems remains unclear. This study numerically investigates the transient flow induced by an array of wall-mounted flexible blades under impulsive metachronal rowing. Two regimes emerge depending on the ratio of natural to rowing frequency, corresponding to linear response and deformation saturation. Maximum transport occurs near Ca = 1, where tip-shed vortices are optimally positioned and captured by neighboring blades, reinforcing thrust. These insights provide guidance for bio-inspired propulsion and microfluidic transport.

[Phys. Rev. Fluids 11, 054103] Published Mon May 18, 2026

Author(s): Binbin Pei, Yayao Zhang, Han Huang, Kunpeng Zhao, and Bofeng Bai

In unstably stratified mixing layers laden with heated particles, analysis of the interphase kinetic energy transfer shows that the contribution of mean power supplied by heated particles to the fluid is stronger than that of the fluctuating part at the early stage, especially near the mixing interfaces. The inclined streaks of particles clustering in the vertical direction become stronger as the flow evolves. As a result, the fluctuating power increases with flow evolution especially near the upper stream, which could be interpreted as the enhancement of updraft buoyancy production and perturbations generated by the inclined streaks.

[Phys. Rev. Fluids 11, 054304] Published Mon May 18, 2026

Author(s): Mohamed Shorbagy and Haithem Taha

Separation from curved surfaces is known to be a viscous phenomenon, governed by boundary layer dynamics. In his 1904 seminal paper, where he introduced the boundary layer, Prandtl hinted at the possibility of having an inviscid separation criterion, “from external conditions” outside the boundary layer. Here, we present a candidate for such a long-sought criterion. We show that there is a unique separation angle that minimizes the curvature in the outer potential flow. Moreover, this minimizing angle coincides with the experimentally observed one in the flow over a circular cylinder in the subcritical regime, where the averaged flow characteristics force are independent of Reynolds number.

[Phys. Rev. Fluids 11, 054702] Published Mon May 18, 2026

Author(s): Omer M. Babiker, Jørgen R. Aarnes, Ali Semati, Amélie Ferran, Yi Hui Tee, R. Jason Hearst, and Simen Å. Ellingsen

Turbulent flows beneath water surfaces control key processes in the Earth system, yet linking the motion of the free surface to subsurface dynamics has relied on numerical simulations at Reynolds numbers far smaller than in natural flows. By combining particle image velocimetry with free-surface profilometry in a laboratory setting, we take a large step towards bridging the gap to real-world flows, reaching Reynolds numbers two orders of magnitude higher than DNS simulations. Surface features remain strongly correlated with subsurface turbulence, with correlations that are near instantaneous but highly nonlocal in space, persisting up to two integral length scales beneath the surface.

[Phys. Rev. Fluids 11, 054802] Published Mon May 18, 2026

Author(s): Kazi Tassawar Iqbal, Daulet Izbassarov, Luca Brandt, and Outi Tammisola

Dispersing a second phase throughout a carrier fluid significantly alters the system’s bulk rheology, a critical consideration for the transport and mixing of multiphase systems comprising elastoviscoplastic (EVP) carrier fluids ubiquitous in industrial processes. This work investigates the role of elasticity and yield stress of the carrier fluid on the bulk rheology of droplet- and bubble-laden suspensions at dilute to semi-dilute concentrations under simple shear. Analysis of the stress budget and the spatial and size distribution of the dispersed phase elucidates the interplay between the carrier fluid’s EVP rheology and dispersed phase dynamics that influence the bulk rheology.

[Phys. Rev. Fluids 11, 053302] Published Fri May 15, 2026

Author(s): Laurent Talon and Dominique Salin

We investigate the flow of discontinuous shear-thickening fluids with S-shaped rheology in confined and disordered geometries. We demonstrate that, due to the emergence of highly viscous structures, such fluids tend to limit the flow rate at a given pressure gradient. In channel geometries containing obstacles, these structures form in the most constricted regions. In porous media, they also occur in the narrowest pore throats, but tend to be arranged transversely to the flow direction, which effectively creates a viscous barrier. We then study the formation and the spanning of these barriers, which exhibit properties similar to those of critical systems.

[Phys. Rev. Fluids 11, 053303] Published Fri May 15, 2026

Author(s): Peter Frick, Andrei Sukhanovskii, Andrei Vasiliev, Sergey Filimonov, and Andrei Gavrilov

Complex mutual interaction between two convective oscillators are studied. A variety of regular and irregular modes are found. The dynamics of large plates strongly depend on the depth of immersion and include convective pendulum mode with regular antiphase oscillations, irregular fluctuations, full stops and synchronized periodic movements. The dynamics of plates of relatively small size is fundamentally different. It is characterized by the modes with a pronounced intermittent character. The very specific behavior was observed during random walks, in which the plates perform small-scale chaotic oscillations, without breaking away from each other, as if they are on a flexible bundle.

[Phys. Rev. Fluids 11, 053501] Published Fri May 15, 2026

Author(s): Gene Patrick S. Rible, Syed Jaffar Raza, Connor K. Traynor, Joshua T. Watkins, Hannah P. Sebek, Alexander R. Bottoms, Tadd T. Truscott, and Andrew K. Dickerson

Our experiments bridge classic raindrop shape theory and the behavior of contaminated drops in atmospheric and industrial aerosols. With two cameras, we reconstruct the three-dimensional shape, orientation, and oscillation of levitated nanofluid drops. Low nanoparticle loading can destabilize the interface whereas higher loading stabilizes it. Surfactant shifts the stability thresholds by sequestering particles.

[Phys. Rev. Fluids 11, 053604] Published Fri May 15, 2026

Author(s): Theo A. Lewy and Rich R. Kerswell

Pressure-driven flow of a dilute polymer solution has been numerically observed to support elastic turbulence which is organized around the interactions of localized versions of two-dimensional arrowhead traveling waves. Here, we isolate these spanwise-localized arrowheads for the first time. We find symmetric and asymmetric states, and identify a process in which these localized states split to spawn multiple arrowheads. These arrowheads have small velocities perpendicular to the flow suggesting they may be poor mixers.

[Phys. Rev. Fluids 11, L051301] Published Fri May 15, 2026

Author(s): Ellen M. Jolley, Daniel J. Booth, and Thomas D. Montenegro-Johnson

We consider hydrogel swelling while confined between two rigid walls in cases of (i) slip and (ii) no slip boundary conditions on the walls. Using the framework of large deformation poroelasticity, we find a fully nonlinear solution numerically in case (i) and a linear solution analytically in case (ii), and show that in case (ii) the hydrogel exerts substantially more force on the walls. This has application in the design of hydrogel-based actuators.

[Phys. Rev. Fluids 11, 053102] Published Thu May 14, 2026

Author(s): Aditya Ganesh, Dario Vincenzi, Ranganathan Prabhakar, and Jason R. Picardo

Brownian dynamics simulations of a bead-spring chain in a turbulent flow show that hydrodynamic interactions (HI) modify the stretching of polymers, owing to hydrodynamic shielding and conformation-dependent drag. HI delays the turbulence-induced migration between coiled and stretched states and alters the distribution of extension. Stiff chains stretch more while highly elastic chains stretch less, in the presence of HI, resulting in a steeper coil-stretch transition. These effects cannot be reproduced by adding HI to a dumbbell, because of its inability to form a physical coil, implying that dumbbell-based descriptions of polymer solutions must incorporate an extension-dependent drag.

[Phys. Rev. Fluids 11, 053301] Published Thu May 14, 2026