Physical Review Fluids

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): 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

Author(s): Chenyu Jiang and George Constantinescu

River confluences play an important role in riverine systems and riverine ecology. Eddy resolving simulations are used to investigate in a systematic way the effect of increasing bed discordance of the minor tributary in a confluence of simplified geometry. Increasing the bed discordance reduces the coherence and number of streamwise oriented vortices forming on the minor tributary side of the mixing interface and promotes the formation of a near-bed intrusion of mixed fluid into the minor tributary side of the main channel near the confluence apex. This is the main mechanism that is responsible for the increase in the rates of mixing between the two streams with increasing bed discordance.

[Phys. Rev. Fluids 11, 053801] Published Mon May 11, 2026

Author(s): Salar Jabbary Farrokhi, Aaron D. Ratschow, and Steffen Hardt

In recent years, the importance of previously overlooked electrostatic effects has opened a new perspective in the field of dynamic wetting. While spontaneous charging has been investigated in sliding drops, here, we show that it can substantially affect capillary wetting instabilities. The capillary breakup of a liquid bridge wetting a surface causes electrostatic charging that slows down the breakup dynamics and leads to spontaneous motion of satellite drops. Our results highlight the central importance of electrostatics in dewetting processes beyond sliding drops.

[Phys. Rev. Fluids 11, 054002] Published Mon May 11, 2026

Author(s): Javier Alaminos-Quesada, Guillermo L. Nozaleda, Cándido Gutiérrez-Montes, and Antonio L. Sánchez

Cerebrospinal-fluid motion and solute transport in the subarachnoid space are strongly influenced by trabeculae. Most existing flow and transport descriptions rely on homogenized porous-media models whose accuracy under physiological oscillatory-flow conditions remains uncertain. This study benchmarks such macroscopic models against direct numerical simulations in a canonical fibrous channel. The main advance is to show that the unsteady Brinkman equation accurately captures the flow field, whereas current quasi-steady transport models fail to represent key unsteady shear-enhanced dispersion mechanisms.

[Phys. Rev. Fluids 11, 054102] Published Mon May 11, 2026

Author(s): Marko Tesanovic, Daniel M. Markiewitz, Marcus L. Popp, Martin Z. Bazant, and Sonja Berensmeier

We present a thermodynamically consistent continuum theory for magnetic-particle transport and capture in high-gradient fields. Derived from a free-energy functional, the model couples magnetism, mass transport, and flow without empirical shutoff rules, so that shielding, anisotropic deposition, and boundary-layer confinement emerge naturally from particle-field feedback. A Mason number phase diagram then organizes capture into thermodynamic, transitional, and dynamic regimes, providing a predictive basis for High-Gradient-Magnetic-Separation design and optimization.

[Phys. Rev. Fluids 11, 054302] Published Mon May 11, 2026

Author(s): Luigi La Ragione, Michele Larcher, James T. Jenkins, and Anna Prati

We measure particle motion in a two-dimensional fluid-saturated granular bed, below a submerged oscillating plate, to test mechanisms responsible for the change in shape of its surface. As the plate moves upward, some grains in a region of the bed are mobilized and dragged by the fluid both vertically and horizontally through a matrix of fixed particles. The measured particle streamlines are fit over many cycles to those in the experiment, using the pressure field in the bed that results from the solution of Darcy’s equation. When different horizontal and vertical permeabilities are used in the Darcy flow relations, we find relatively good agreement with the predictions of the mixture flow.

[Phys. Rev. Fluids 11, 054303] Published Mon May 11, 2026

Author(s): L. S. Merlo, L. Kadem, W. Saleh, H. D. Ng, and G. Di Labbio

Twin pulsed jets are highly efficient at transferring energy, making them particularly attractive for applications ranging from underwater propulsion and maneuvering to the filling of heart cavities. However, little is known about their dynamic interactions within a hemispherical elastic cavity. Distinct flow regimes are identified here based on formation time and jet spacing. These regimes include short-time decay, decay at the lower wall, wall rebound, and wall rebound with secondary vortices. These findings enhance our understanding of the complex flow patterns generated by certain medical devices and pathological conditions, as well as their effects on cardiac function and performance.

[Phys. Rev. Fluids 11, 054701] Published Mon May 11, 2026

Author(s): Bauyrzhan K. Primkulov

The size of a detaching pendant drop is set by Tate’s law and depends only weakly on the nozzle radius. Here, we show that simple geometric confinement can trigger early detachment at significantly reduced volumes by introducing an additional capillary force. A minimal scaling law collapses the data across geometries, providing a robust and passive route to tune drop size without external actuation.

[Phys. Rev. Fluids 11, L051601] Published Mon May 11, 2026

Author(s): Ehud Yariv

When the solute concentration is different in the two sides of a semipermeable membrane, solvent flows from the solute-depleted side to the solute-enriched side. More generally, when a vesicle is placed in a solute-concentration gradient, it experiences inward osmosis on the low-concentration side and outward osmosis on the high-concentration side. This paper investigates the resulting motion of the vesicle down the gradient.

[Phys. Rev. Fluids 11, 053603] Published Thu May 07, 2026

Author(s): Demosthenes Kivotides

Quantized vortex filaments in Bose superfluids act as line-like sources for microhydrodynamic (low Reynolds number) normal-fluid motion on scales that standard turbulence grids cannot resolve. We develop a two-level multiscale framework that couples a filtered normal-fluid solver to an explicit microhydrodynamic Stokes Linear Response (LRT), incorporating these effects self-consistently into both vortex dynamics and the resolved normal-fluid equations. The approach enables efficient superfluid-turbulence computations for laboratory, cryogenic, and astrophysical settings.

[Phys. Rev. Fluids 11, 054602] Published Thu May 07, 2026

Author(s): Swapnil Soni and Avishek Ranjan

We derive a new theoretical estimate of the root mean square velocity of the electro-vortex flow (EVF) – a current-driven MHD flow – for high Reynolds number regime using an inertia-Lorentz balance in the vorticity transport equation. This estimate accounts for the dimension of the current collector, an important parameter that governs the EVF. There is an excellent agreement between the theory and numerical simulations performed using the custom-built code in OpenFOAM. We also explain the EVF characteristics using these results. Our numerical results reveal a distinct flow feature stemming from the domain finiteness at relatively higher current collector radii.

[Phys. Rev. Fluids 11, 053701] Published Wed May 06, 2026

Author(s): W.-P. Breugem and Y. E. Kamis

We investigated the dynamics of a Newtonian liquid jet issued from a long circular nozzle into a gaseous environment. While the jet contracts at high Reynolds number, it swells at low Reynolds number. To analyze this, we derived an integral momentum balance for the flow in both the nozzle and jet. The swell at low Reynolds number is associated with an excess integral wall shear stress near nozzle exit relative to perfect Poiseuille flow. Numerical simulations revealed self-similar behavior of the flow within the nozzle, which is explained from the stick-slip transition at the nozzle lip and the subsequent development of a boundary layer along the jet interface.

[Phys. Rev. Fluids 11, 054101] Published Wed May 06, 2026

Author(s): Morie Koseki and Marco Edoardo Rosti

This study investigates the effect of compliant walls on the turbulent heat transfer in channel flows over viscous-hyperelastic walls. We show that the compliant wall leads to an increase not only of the momentum transfer but also of the heat transfer, and that the heat transfer enhancement is favorable compared to the momentum one

[Phys. Rev. Fluids 11, 054301] Published Wed May 06, 2026

Author(s): Pabitra Badhuk, Atanu Dolai, and R. V. Ravikrishna

Twin-swirl flows can generate various vortex breakdown structures depending on the swirling direction, strength, and the momentum ratio between the swirling streams. The present study uses scale-resolving simulations to analyze the mechanism of radial pressure gradient formation, role of entrainment in mixing, and identification of coherent structures in such flows. We show that while the centripetal acceleration dominates the radial pressure gradient formation with a single swirler, the contribution of advection and turbulence components are also significant in twin-swirl flows. We also show that the entrainment velocity is better estimated by the rms components than the mean velocity.

[Phys. Rev. Fluids 11, 054601] Published Wed May 06, 2026