Latest papers in fluid mechanics

Author(s): James D. Shemilt, Alice B. Thompson, Alex Horsley, Carl A. Whitfield, and Oliver E. Jensen

The surface-tension-driven instability of a liquid film coating a vertical tube can lead to the formation of liquid collars that drift downwards under gravity. This scenario is relevant to the flow of mucus in lung airways. Using thin-film theory, we investigate the formation and motion of collars when the liquid film is viscoplastic. In the limit of weak gravity relative to capillary effects, we quantify the reduction in steady collar speed due to viscoplasticity, and identify conditions under which viscoplastic collars translate steadily, whilst steady motion does not occur in the Newtonian case.

[Phys. Rev. Fluids 10, 103301] Published Wed Oct 22, 2025

Author(s): Abhijit Kumar Kushwaha, Sankara Arunachalam, Ville Jokinen, Dan Daniel, and Tadd T. Truscott

Seven superimposed images capture the motion of a 42 μL water droplet sliding down an inclined superhydrophobic surface. Upon deposition, the droplet partially wets the surface, with interferometry revealing a heterogeneous distribution of white and black patches characteristic of the Cassie–Baxter state. As the droplet accelerates and reaches higher velocities, it entrains air from the surroundings, forming a thin lubricating air layer beneath it. This air layer thickens progressively with increasing velocity, and once a critical threshold is exceeded, the droplet transitions into a state of aerodynamic levitation.

[Phys. Rev. Fluids 10, 103603] Published Wed Oct 22, 2025

Author(s): Vadim Travnikov and Christoph Egbers

The study of large-scale convective flows within a spherical gap has been the focus of numerous theoretical and numerical investigations because of its relevance to geophysical applications. This is particularly true in scenarios where the inner surface is warmer than the outer surface, and the flui…

[Phys. Rev. E 112, 045109] Published Wed Oct 22, 2025

Author(s): Tomas Fullana, Stéphane Zaleski, and Gustav Amberg

Dynamic wetting poses a well-known challenge in classical sharp-interface formulation as the no-slip wall condition leads to a contact line singularity that is typically regularized with a Navier boundary condition, often requiring empirical fitting for the slip length. On the other hand, this parad…

[Phys. Rev. E 112, 045108] Published Tue Oct 21, 2025

Author(s): Takahiro Kanazawa and Kenta Ishimoto

Crawling animals like snails and slugs move by generating waves along their bodies over thin layers of fluid. Using lubrication theory, we derived a general formula for locomotion speed when the viscosity of the fluid layer varies in space and showed that the model captures two common locomotion patterns: transverse and longitudinal crawling. Furthermore, through multiple-scale perturbation expansions, we analytically demonstrate how position-dependent viscosity can slow locomotion, depending on the crawling gait and direction of motion. The results reveal nonlinear, accumulative mechanical interactions between locomotion and a heterogeneous environment.

[Phys. Rev. Fluids 10, 103102] Published Tue Oct 21, 2025

Author(s): Sidyant Kumar, Sachchida Nand Tripathi, and Sanjay Kumar

Atomization of liquid drops has practical engineering applications such as in combustion, sprays, and others. We experimentally study the shear stripping mode of atomization where a liquid drop interacts with a normal shock wave and deforms under shock-induced flow. The initial deformation and circumferential surface waves on the drop are governed by shear instability (Kelvin-Helmholtz). The wave amplification redistributes liquid and the drop evolves into a bowl. Flow acceleration induces modulations, forming an azimuthal ring with its own rim. Two sub-modes emerge: Ligament mode with sheet shearing at lower velocities, and Cellular mode with localized cells at relatively higher velocities.

[Phys. Rev. Fluids 10, 103602] Published Tue Oct 21, 2025

Author(s): Yuchen Ye (叶宇晨), Yan Yang (杨艳), Bin Jiang (蒋彬), Cheng Li (李程), Minping Wan (万敏平), Yipeng Shi (史一蓬), and Sean Oughton

We investigate how finite Reynolds number affects the width of the Inertial Range (IR) in magnetohydrodynamic (MHD) turbulence. A set of high-resolution incompressible MHD simulation data is employed, with Taylor Reynolds Number Reλ ranging from about 200 to 400. The IR width is quantified using third-order laws. A semi-empirical model for second-order structure functions is established and applied to the MHD von Karman-Howarth equation, determining IR boundaries for given Reynolds numbers. This model allows extrapolation of Reλ beyond the reach of current simulations or experiments. We suggest that establishing a two-decade IR in MHD turbulence requires Reλ to be at least 1,500.

[Phys. Rev. Fluids 10, 103703] Published Tue Oct 21, 2025

Author(s): Max Herzog and Jesse Capecelatro

We present results from direct numerical simulations of turbulent channel flow laden with adhesive (viscoelastic) particles. Particles demonstrate higher adhesion strengths at elevated temperatures, an effect we probe by varying the adhesion number. Using spanwise radial distribution functions, we show that particle heterogeneity near and on the wall is promoted by turbulence. Furthermore, low-adhesion, high-inertia particles demonstrate spanwise creep along the wall, leading to elongated streamwise deposits. Abrasive wear profiles highlight the consequences of heterogeneity, with local wear exceeding ten times the mean.

[Phys. Rev. Fluids 10, 104302] Published Tue Oct 21, 2025

Author(s): Lokendra Mohan Sharma, Harish N. Dixit, and Lakshmana Dora Chandrala

While immiscible liquid jets play vital roles in applications from chemical reactors to environmental flows, understanding their dynamics has been hindered by optical distortions at fluid interfaces. Using simultaneous Particle Image Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF) with refractive index-matched fluids, this study provides comprehensive experimental validation of both inviscid and viscous analytical models for buoyant liquid-in-liquid jets in the laminar regime. The study uncovers two distinct scaling regimes: an inertia-dominated near field and a viscosity-governed far field, with buoyancy and jet Reynolds number controlling dynamics while surface tension and outer-phase viscosity play minor roles.

[Phys. Rev. Fluids 10, 104303] Published Tue Oct 21, 2025

Author(s): Samuel Kok Suen Cheng and Jian Sheng

The reconstruction of the conserved scalar from gradient field like pressure is important in many applications. Most current direct integration algorithms initiate the integration at the domain boundaries, where gradient measurement is often unreliable. This study proposes the Boundary-Independent Shortest Path (BISP) integration method, which initiates at an internal node and grows outwards towards the boundaries, thereby eliminating any dependency on the boundaries. This integration algorithm can be directly applied to pressure gradient fields containing inner voids of arbitrary shapes and sizes without compromising the accuracy.

[Phys. Rev. Fluids 10, 104604] Published Tue Oct 21, 2025

Author(s): Alexander S. Balankin

Fractal features of permeable (e.g., porous or/and fractured) medium strongly affect the imbibition behavior in the Lucas-Washburn-like scaling regime. Mapping a spontaneous imbibition in a fractally permeable medium onto a fractal continuum flow allows us to establish the relations between the imbi…

[Phys. Rev. E 112, 045107] Published Mon Oct 20, 2025

Author(s): F. Zabaleta, B. Bornhoft, S. S. Jain, S. T. Bose, and P. Moin

Accurate heat transfer prediction on rough surfaces is critical for ice accretion prediction and aviation safety. Using high-fidelity simulations of conjugate heat transfer, we resolve heat transport in both the fluid and a low-conductivity solid featuring laser-scanned ice roughness. Contrary to the behavior of isothermal surfaces, the low thermal conductivity of the solid causes roughness crests to become the coolest points, sometimes even drawing heat from the air. This work highlights the necessity of including solid conduction effects in next-generation icing models.

[Phys. Rev. Fluids 10, 104603] Published Mon Oct 20, 2025

Author(s): W. G. Rodrigues, Jr. and V. B. Henriques

Nanoporous capsules have been the subject of intense investigation in the field of drug delivery. One of the essential properties of such particles, which requires characterization, is their structure. Many experimental techniques have been used for this purpose, such as wide-angle neutron or x-ray …

[Phys. Rev. E 112, 045106] Published Fri Oct 17, 2025

Author(s): Wei Cai, ShuaiShuai Jiang, He Wang, Pei Wang, DongJun Ma, and Ting Si

While shock-tube experiments on the Richtmyer-Meshkov instability (RMI) have been extensively conducted under weak-shock conditions, such experiments under strong-shock conditions remain rare. This study presents the first shock-tube experiments on RMI at V-shaped interfaces driven by shocks with Mach numbers exceeding 3.0, demonstrating that interface evolution depends on initial amplitude and involves compressibility, Mach-reflection, shock-proximity, and secondary-compression effects absent under weak-shock conditions. These effects render existing linear and nonlinear models inadequate. Guided by present experimental findings and physical understanding, empirical models are developed.

[Phys. Rev. Fluids 10, 104005] Published Thu Oct 16, 2025

Author(s): Yangyang Sha, Yuhang Xu, Yingjie Wei, Xiaojian Ma, and Cong Wang

In fluid experiments, obtaining velocity fields at high temporal resolution is often prohibitively expensive. This study introduces a semi-supervised deep learning framework that leverages low-cost, high-speed cavitation phase imaging to eliminate the need for high-frequency velocity labels. Applied to cavitating hydrofoil flows, the method reconstructs temporally super-resolved velocity fields from sparse, low-frequency samples and demonstrates robust generalization under unsteady conditions. These results highlight an efficient and economical approach for modeling complex multiphase flows.

[Phys. Rev. Fluids 10, 104301] Published Thu Oct 16, 2025

Author(s): Li Wei, Xiaoxian Guo, and Xuefeng Wang

Deep learning models for particle imaging velocimetry (PIV) often suffer from complex, black-box architectures that limit efficiency and real-world generalization. We propose a physics-informed variational framework that explicitly embeds classical fluid principles, like incompressibility, into its multi-scale inference structure. This principled design eliminates the need for complex black-box components and achieves new state-of-the-art accuracy on challenging flows. Crucially, the model shows outstanding generalization, applying directly to riverine data without retraining, defining a new path for robust and physically consistent flow measurement.

[Phys. Rev. Fluids 10, 104902] Published Thu Oct 16, 2025

Author(s): Rizwan Ullah, Andres Barrio-Zhang, and Arezoo M. Ardekani

Acoustic pressure nodes in acoustophoretic devices are crucial for applications in tissue engineering, cell analysis, and particle trapping. Typically, a single primary node forms at the half-wavelength resonance condition, with its shape and position constrained by the channel dimensions. The gener…

[Phys. Rev. E 112, 045105] Published Thu Oct 16, 2025

Author(s): G. Le Doudic, M. Jafari, J. Barckicke, S. Perrard, and A. Eddi

Polar regions are covered by sea ice, which can be seen as a thin solid elastic sheet with heterogeneous mechanical properties. The dynamics of deformation of a floating solid sheet is primarily governed by gravity, water density, and the flexural modulus, which depends on its mechanical properties,…

[Phys. Rev. E 112, 045104] Published Wed Oct 15, 2025

Author(s): Oscar Flores and Manuel Garcia-Villalba

While biological systems like dragonflies and schooling fish achieve remarkable performance through coordinated hydrodynamic interactions, the current understanding of the underlying mechanisms remains incomplete. This review examines how vortex dynamics, structural flexibility, and 3D effects influence performance in tandem flapping wing systems. It is shown that for tandems of spanwise-flexible wings, the forewing achieves maximum thrust through fluid-structure resonance while moderately stiff hindwings effectively capture upstream wake structures leading to increased overall performance. The mechanisms by which self-propelled systems achieve energy savings are also discussed.

[Phys. Rev. Fluids 10, 100502] Published Wed Oct 15, 2025

Author(s): Thibault Maurel-Oujia and Kazuki Maeda

Nonequilibrium reactive molecular dynamics simulations reveal detailed structures of a Mach 5 shock wave in a gaseous H2/O2 mixture, driven by the large mass disparity between H2 and O2 molecules.

[Phys. Rev. Fluids 10, 103201] Published Wed Oct 15, 2025