Latest papers in fluid mechanics

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

Author(s): David J. Lusher and Andrea Sansica

Transonic buffet is a shock-wave/boundary-layer interaction on wings involving coexisting and self-sustained 2D chordwise shock motion and 3D separation-driven spanwise buffet-cell dynamics. Using implicit LES and spectral modal analysis of infinite swept wings up to aspect ratio 3, we show that the 2D shock mode is insensitive to sweep, while sweep transforms a quasistationary low-frequency 3D mode at unswept conditions into a spanwise-travelling mode. The 3D mode shifts monotonically to higher Strouhal numbers with increasing sweep while retaining a fixed spanwise wavelength, and pronounced buffet cells are shown to arise only when mean flow separation at the shock is sufficiently strong.

[Phys. Rev. Fluids 11, 053401] Published Thu May 14, 2026

Author(s): Jun Gao, Xiaocong Yang, Senlin Zhu, Qingfei Fu, and Lijun Yang

This work investigates the dynamics of thick liquid films flowing down vertical fibres with insoluble surfactants. A one-dimensional long-wave model, validated against the full two-dimensional system, reveals three stability regimes depending on the Marangoni number (Ma): Rayleigh–Plateau dominated at low Ma, complete stabilization at intermediate Ma, and Marangoni-induced instability at high Ma. Nonlinear analysis shows these behaviors result from the competition between Marangoni convection and the difference between interface velocity and wave speed, providing new insight into surfactant-controlled film stability.

[Phys. Rev. Fluids 11, 053901] Published Thu May 14, 2026

Author(s): Qisong Xie, Feifei Qin, Xiao-Peng Chen, Xiaowen Shan, and Haibao Hu

While Ostwald ripening is widely studied, its reaction-controlled regime on unpinned substrates lacks a rigorous analytical foundation. Here, the authors establish a theoretical framework by deriving the kinetic equations and explicit bubble growth rates under constant contact angle conditions. Validated by Lattice Boltzmann simulations, their theory reveals a striking “reversed volume ripening” on heterogeneous substrates, where a smaller-volume bubble completely consumes a larger one. This fundamentally proves that ripening is governed by curvature-driven chemical potential rather than volume.

[Phys. Rev. Fluids 11, 054003] Published Thu May 14, 2026

Author(s): Eiichi Sasaki, Javier Jiménez, and Genta Kawahara

Unstable periodic orbits provide a dynamical-systems view of coherent structures in wall-bounded turbulence. In large-eddy simulations of plane Couette flow, we identify an orbit in which streamwise rolls trigger streak instability, generate spanwise vortices, and stretch them toward the wall. The associated Lyapunov vectors localize in high-strain shear layers, linking vortex dynamics to orbital instability.

[Phys. Rev. Fluids 11, 054603] Published Thu May 14, 2026

Author(s): Jiyang He and Yan Wang

In final states of freely decaying two-dimensional turbulence over topography, background flows follow a linear potential vorticity (PV)-streamfunction relationship, but localized vortices have remained poorly understood. We show that the vortices locked to topographic bumps and dips follow a robust, “sinh”-like relationship. We propose an empirical model—a superposition of topographic background flow and Gaussian vortices—that accurately reproduces the quasistationary final states. Linear stability analyses of these stationary vortex solutions explain the observed vortex-topography correlations across different energy levels.

[Phys. Rev. Fluids 11, 054801] Published Thu May 14, 2026

Author(s): Qi Wang and Zejian You

Identifying the origin of dangerous events and perturbations in fluid systems is a central challenge in many inverse problems. This work develops a unified framework combining linear and quadratic sensitivity analysis to create a positional embedding for one-shot localization of sources in weakly nonlinear flows, with unknown intensity. By extending classical adjoint-based approaches beyond the linear regime, the method significantly improves accuracy and efficiency in detecting sources under nonlinear interactions in fluid systems.

[Phys. Rev. Fluids 11, 054901] Published Thu May 14, 2026

Author(s): Yoav Tsori and Hannes Uecker

We present a theoretical framework for unidirectional electromagnetohydrodynamic flow of dilute electrolytes under perpendicular magnetic fields. Starting from the Navier-Stokes equation coupled with the Poisson-Nernst-Planck formulation, we show that the problem admits a sequential decoupling: the …

[Phys. Rev. E 113, 055105] Published Mon May 11, 2026

Author(s): Christian Tantardini and Fernando Alonso-Marroquín

We develop a quantitative framework to determine the minimal periodic supercell required for representative simulations of capillarity-screened Darcy flow in stationary random, polydisperse granular media. The microstructure is characterized by two-point statistics (covariance and spectral density) …

[Phys. Rev. E 113, 055106] Published Mon May 11, 2026

Author(s): Ursy Makanga, Akhil Varma, and Panayiota Katsamba

In this paper, we have identified and characterized a novel route to self-propulsion in which spontaneous shape changes give rise to symmetry-breaking in autophoretic colloids. By means of theoretical predictions and numerical simulations, we show that a deformable autophoretic filament with a uniform chemical profile, i.e., that is otherwise immotile, can achieve self- propulsion via a buckling instability. Our findings provide physical insight into the design of reconfigurable synthetic microswimmers and bio-inspired materials for applications such as cargo transport, drug delivery, or tissue scaffolding.

[Phys. Rev. Fluids 11, 053101] Published Mon May 11, 2026