New Papers in Fluid Mechanics

Author(s): Florian Kogelbauer and Ilya Karlin

We demonstrate that the Chapman-Enskog series is locally equivalent to the exact spectral closure defined on slow kinetic eigenmodes in the limit of vanishing Knudsen number. We further show that the Chapman-Enskog series diverges everywhere except at the global equilibrium for an explicit example, …

[Phys. Rev. E 113, 045105] Published Tue Apr 14, 2026

Author(s): Christopher Triola

The Madelung equations offer a hydrodynamic description of quantum systems, from single particles to quantum fluids. In this formulation, the probability density is mapped onto the fluid density and the phase is treated as a scalar potential generating the velocity field. As examples of potential fl…

[Phys. Rev. E 113, 045104] Published Mon Apr 13, 2026

Author(s): Rauoof Wani and Sanat Tiwari

Turbulence in viscoelastic media is typically associated with polymeric fluids, where elasticity drives chaotic flows even at low Reynolds numbers. Here, we demonstrate that strongly coupled plasmas, despite lacking molecular chains, exhibit intermittent viscoelastic turbulence arising from long-range inter-particle interactions. Using large-scale three-dimensional molecular dynamics simulations, we uncover a cascade of kinetic and elastic energy with steeper power-law scaling than Kolmogorov k−5/3 and intermittency. These results establish dusty plasmas as a microscopic platform for exploring viscoelastic turbulence beyond conventional fluid systems.

[Phys. Rev. Fluids 11, 043301] Published Mon Apr 13, 2026

Author(s): Tristan Aurégan, Noé Daniel, Megan Mazzatenta, and Luc Deike

When bubbles burst at the surface, they eject droplets through the formation of a fast upwards jet. We study how this jet is modified when bubbles are grouped together in rafts at the surface, and find that the presence of these neighbors strongly reduces the size of the ejected droplets and increases their upwards velocity. This effect significantly broadens the drop size distribution of the whole raft and shifts the peak towards smaller sizes.

[Phys. Rev. Fluids 11, 043601] Published Mon Apr 13, 2026

Author(s): Weiyu Shen, Yuchen Ge, Zishuo Han, Yaomin Zhao, and Yue Yang

Wall-bounded turbulence exhibits coherent vortical structures whose geometry and multiscale organization remain difficult to capture in physics-based models. We construct turbulence fields as ensembles of hierarchically organized hairpin vortex packets with height-dependent core size. The model quantitatively reproduces statistical and structural features of high-Reynolds-number turbulence, including both attached and detached motions. It further elucidates how vortex geometry and packet organization govern these features, while enabling rapid initialization of fully developed turbulence at substantially reduced cost.

[Phys. Rev. Fluids 11, 044604] Published Mon Apr 13, 2026

Author(s): Dongheyu Zhang, Junkang Mao, Peng Zhang, John P. Verboncoeur, and Yangyang Fu

Laser-sustained plasma (LSP) is a novel light source for bright-field wafer defect inspection in chip manufacturing, but the inherent spatiotemporal instabilities severely limit performance. Through experiments and multiphysics modeling, this work reveals that these periodic fluctuations originate from buoyancy-driven vortex ring dynamics. A generalized scaling law incorporating the gas density ratio is established for accurate frequency prediction, demonstrating that the Prandtl and Péclet numbers govern the oscillation threshold and patterns. These findings provide a mechanistic framework for the development of stable LSP light sources.

[Phys. Rev. Fluids 11, 044701] Published Mon Apr 13, 2026

Author(s): Luiz Eduardo Czelusniak, Tim Niklas Bingert, Stephan Simonis, Alexander J. Wagner, and Mathias J. Krause

An analytical solution based on a diffuse-interface model is presented for an isothermal evaporation problem at subsaturated vapor pressure. The macroscopic equations are derived from the free-energy formulation widely used in the lattice Boltzmann literature, distinguishing our approach from conven…

[Phys. Rev. E 113, 045103] Published Fri Apr 10, 2026

Author(s): Jie Sun, Yicun Wang, Shumeng Xie, Salim M. Shaik, and Huangwei Zhang

Building on prior studies of obstacle–detonation interactions, this work uses two-dimensional detailed-chemistry simulations to examine how obstacle configurations affect detonation attenuation and flame acceleration. Increased dispersion enhances attenuation by fragmenting the front and leads to distinct reinitiation modes compared to concentrated obstacles. With extended obstacle sections, propagation transitions from quasi-detonation to choking, governed by a critical blockage ratio that decreases with increasing cell width. A scaling is proposed to predict regime transitions and capture the balance between shock attenuation and flame acceleration.

[Phys. Rev. Fluids 11, 043201] Published Thu Apr 09, 2026

Author(s): Feng Ren, Yuanpu Zhao, Jian Song, Boo Cheong Khoo, Yongdong Cui, Zhaokun Wang, and Dong Song

Deep reinforcement learning (DRL) for active flow control in turbulent regimes has been challenging due to prohibitive computational costs. This study overcomes this barrier by integrating a GPU-accelerated lattice Boltzmann solver with a two-stage exploration strategy, making DRL feasible for turbulent flow applications. For the canonical case of flow past a circular cylinder, the DRL-guided controller reduces drag by 55% and lift fluctuation by 26%, through significantly modifying the wake dynamics and turbulent features. Follow-up tests demonstrate that online-smoothed actuation performs as effectively as high-frequency inputs, offering practical advantages for real-world implementation.

[Phys. Rev. Fluids 11, 043903] Published Wed Apr 08, 2026

Author(s): Siyi Li, Zihao Zhu, Lei Xie, Yaguang Xie, Ruonan Wang, Qiang Du, and Junqiang Zhu

Under transient conditions, the evolution of flow in the rotor-stator cavity of an aero-engine differs markedly from the steady state. Using theory together with three-dimensional direct numerical simulations, we capture the nonlinearity and unsteady behavior in the transient evolution of rotating cavity flows. For a laminar enclosed rotor-stator cavity, the transient process primarily generates and dissipates circular waves whereas a turbulent one features small-scale fragmented vortical structures. This study elucidates three-dimensional transient evolution and flow structures in rotating cavities, providing a foundation for further investigations of transient rotating cavity flows.

[Phys. Rev. Fluids 11, 043904] Published Wed Apr 08, 2026

Author(s): Rongji Hu, Zhikang Huang, Geng Zhao, Xue-Lu Xiong, Feng Liu, Jian Fang, and Yi Zhou

The generation of skin friction in a spatially evolving turbulent boundary layer at a Mach number Ma∞=2.9 is analyzed using direct numerical simulation (DNS). Particular attention is paid to clarifying the impact of the turbulent/nonturbulent interface (TNTI) height on the skin friction. In contrast…

[Phys. Rev. E 113, 045102] Published Tue Apr 07, 2026

Author(s): M. Etchevest, P. Dmitruk, S. Karmakar, B. Semin, R. Godoy-Diana, and J. E. Wesfreid

Transition to turbulence in wall-bounded shear flows is often explained through the self-sustaining process proposed by Waleffe, where streaks, streamwise vortices, and streak waviness interact nonlinearly. Using direct numerical simulations of plane Couette–Poiseuille flow near transition, we examine how streak waviness relates to the underlying roll structures. The results show that, once the rolls reach sufficient amplitude, the waviness of the streaks scales quadratically with the rolls, clarifying a key nonlinear step of the self-sustaining process in this asymmetric shear flow.

[Phys. Rev. Fluids 11, 044603] Published Tue Apr 07, 2026

Author(s): Rundong Zhou, Adrien Lefauve, Roberto Verzicco, and Detlef Lohse

What bridges convection and stratified turbulence? Using direct numerical simulations, we reveal that in highly turbulent stratified inclined duct (SID) flow, these two phenomena can coexist within a single canonical system. At sufficiently large Reynolds number, SID undergoes a transition to the ultimate regime of turbulent convection, marked by the enhanced transport scaling Nu~Ra1/2. The transition coincides with the onset of turbulent boundary layers and is subcritical and hysteretic, as expected for the non-normal-nonlinear route to turbulence in shear flows.

[Phys. Rev. Fluids 11, 044802] Published Tue Apr 07, 2026

Author(s): Talha Mushtaq and Maziar S. Hemati

Spatially localized flow perturbations that maximize perturbation-energy amplification can reveal underlying drivers of flow instability. In this paper, we show that such spatially localized perturbations can be found by solving a particular sparse optimization problem and propose an efficient iterative method for doing so. Our approach is demonstrated on a subcritical plane Poiseuille flow, wherein we find that a subset of the perturbations identified by our method yield a comparable degree of energy amplification as their global counterparts.

[Phys. Rev. Fluids 11, 043901] Published Mon Apr 06, 2026

Author(s): Martin Oberlack, Kilian Vinzenz Wilhelm, Simon Görtz, Johannes Conrad, Alparslan Yalcin, Lara De Broeck, and Yongqi Wang

We revisit Squire’s theorem, a fundamental concept in hydrodynamic stability theory, but only valid for temporal modes, and extend it to spatiotemporal modes. This extension reveals a new class of subcritical oblique modes in which three-dimensional disturbances can become unstable at lower Reynolds numbers than their two-dimensional equivalents. While individual modes are unphysical, their superposition within a framework such as Briggs’ theory yields finite-energy perturbations. The theory provides a framework to describe spatially growing oblique structures, such as those observed in transitional shear flows.

[Phys. Rev. Fluids 11, 043902] Published Mon Apr 06, 2026

Author(s): Charul Gupta, Venkata Sai Anvesh Sangadi, Lakshmana Dora Chandrala, and Harish N Dixit

Experiments and numerical simulations of flow near a moving contact line are presented for dynamic contact angles exceeding 90°. High-resolution PIV and interface tracking deliver simultaneous measurements of velocity fields, interface shapes, and interfacial speeds across low to moderate Reynolds numbers. A central finding is the pronounced slowing down of fluid particles along the interface as they approach the contact line, providing direct experimental evidence toward resolving the classical singularity. Complementary VOF simulations with a variable-slip model reproduce the observations and demonstrate that such simulations can resolve detailed flow fields with experimental fidelity.

[Phys. Rev. Fluids 11, 044001] Published Mon Apr 06, 2026

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