Physical Review Fluids

Author(s): Gunnar G. Peng, Ehud Yariv, and Ory Schnitzer

This study investigates shear-driven flow over a microstructured surface of zero-thickness ridges separating rectangular grooves infused with a relatively low-viscosity lubricant. Asymptotic analysis in that limit reveals that viscous resistance is dominated by a boundary layer about the ridge tips that is exponentially small in the viscosity ratio μ≪1, resulting in a surprising μ−1/2 scaling for the effective slip length.

[Phys. Rev. Fluids 11, 044201] Published Mon Apr 06, 2026

Author(s): Eric Ibarra, Fabien Candelier, and Gautier Verhille

From previous studies on rigid isotropic particles, one might expect that heavy particles would be centrifuged out of vortices. However, during experimental runs, we observed thin, heavy, flexible discs trapped in stable orbits near a vortex core. By reconstructing their three-dimensional shape and motion, we show how deformability and anisotropy alter the classical force balance. The results raise new questions about how form and flexibility impact transport in vortical flows.

[Phys. Rev. Fluids 11, 044302] Published Mon Apr 06, 2026

Author(s): Kirill Goncharuk, Saichand Chowkampally, Yuri Feldman, and Oz Oshri

The relaxation of a buckled elastic sheet in a fluid involves a balance between bending, inertia, and hydrodynamic forces. We show that a minimal inviscid model predicts both the oscillation frequency about the stable mode and the growth rate of unstable modes, in agreement with more general viscous simulations. The framework also captures the temporal transition from unstable to stable configurations.

[Phys. Rev. Fluids 11, 044401] Published Mon Apr 06, 2026

Author(s): Zishuo Han, Weiyu Shen, and Yue Yang

We model turbulence using coherent vortices distributed within a multiscale statistical framework, termed woven turbulence, which naturally captures key turbulence features. Based on explicitly controllable vortices, we find that the scale-independent hierarchical vortex density corresponds to the −5/3 law of the energy spectrum, while the Reynolds-number-independent total vortex density corresponds to the intermittent scaling of the structure function. Woven turbulence also serves as a fast turbulence synthesis method, requiring only the Taylor-Reynolds number as input and exhibiting extremely low computational cost comparable to the random Fourier modes method.

[Phys. Rev. Fluids 11, 044602] Published Mon Apr 06, 2026

Author(s): Prem Chand Chandolu and Balachandra Suri

Horizontally driven shallow electrolyte flows are widely employed laboratory analogs of oceanic and two-dimensional flows. Although previous studies investigated the presence of three-dimensional circulations within the bulk of turbulent shallow flows, relatively little attention was paid to whether the fluid layer thickness itself remains spatiotemporally uniform. In this study, we report experimental measurements of free-surface deformations in shallow flows. For certain Reynolds number and fluid layer height combinations that characterize the flow, we show that the free surface undergoes significant deformation, thereby rendering an otherwise shallow flow geometrically three-dimensional.

[Phys. Rev. Fluids 11, 044801] Published Mon Apr 06, 2026

Author(s): Qiwei Chen and C. Ricardo Constante-Amores

Rayleigh–Bénard convection is a canonical system for studying turbulent heat transport, yet controlling it at high Rayleigh numbers remains computationally prohibitive. Here, we combine data-driven manifold dynamics with reinforcement learning to construct a reduced-order environment that enables efficient training of control policies. When deployed in direct numerical simulations, the learned strategies achieve up to 23% reduction in heat transfer by stabilizing near-wall dynamics and suppressing plume emission. This work establishes a scalable and physically interpretable route to controlling high-dimensional turbulent flows.

[Phys. Rev. Fluids 11, 044903] Published Mon Apr 06, 2026

Author(s): Githin Tom Zachariah and Harry E. A. Van den Akker

The Lattice Boltzmann Method (LBM) exploits its nearly incompressible nature to relate local density to pressure, avoiding iterative Poisson solvers. However, this pressure–density coupling makes robust extension of LBM to the Two-Fluid equations particularly challenging. In this work, we propose two complementary approaches to address this problem: a mixture model for dilute suspensions prioritizing computational efficiency, and a well-balanced formulation employing a pressure-free LBM with an explicit Poisson solver for maximum accuracy. Both methods are validated on standard benchmarks and isotropic turbulent flows, demonstrating accuracy and robustness across challenging flow regimes.

[Phys. Rev. Fluids 11, 044904] Published Mon Apr 06, 2026

Author(s): Marco Raiola and Jochen Kriegseis

Advective flows are often characterized by wavepackets. Hilbert proper orthogonal decomposition (HPOD) extracts these coherent structures from flow field data by exploiting their representation as modulated traveling waves. HPOD is a complex valued extension of proper orthogonal decomposition, where the analytic signal is obtained via a Hilbert transform applied either in time (conventional HPOD) or along the advection direction (space-only HPOD). Both HPOD formulations yield equivalent decompositions for advecting wavepackets. The resulting modes exhibit amplitude and frequency modulation in space and time, enabling instantaneous, local flow analysis.

[Phys. Rev. Fluids 11, 044905] Published Mon Apr 06, 2026

Author(s): Ankit Gautam and Tim Berk

The decay of turbulent kinetic energy is strongly influenced by large-scale coherent structures. Using a synthetic-jet-driven turbulence facility and the Proper Orthogonal Decomposition (POD) method, we show that slowly decaying modes persistent across repeated experiments bias the observed decay rates. Removing these modes reveals a stochastic turbulence field with decay consistent with classical theory. This framework helps resolve discrepancies in reported decay rates and distinguishes whether variations arise from specific coherent modes or changes in the underlying stochastic turbulence.

[Phys. Rev. Fluids 11, 044906] Published Mon Apr 06, 2026