Physical Review Fluids

Author(s): Caroline Cardinale, Steven L. Brunton, and Tim Colonius

Spectral proper orthogonal decomposition (SPOD) finds orthogonal space-time modes that best capture the 2nd order statistics of a data set. However, SPOD is limited to uniform time-resolved data. Many experimental systems are limited by camera speed. Leveraging the relaxed requirement of pairwise data for dynamic mode decomposition (DMD), we propose a pairwise SPOD algorithm that estimates SPOD modes of nonuniformly sampled data. Using 2 PIV setups in tandem, the time delay within a data pair satisfies the Nyquist criterion, but the time between pairs does not, allowing time to process the last snapshot. Computational data is used for validation and the algorithm is of general use.

[Phys. Rev. Fluids 10, 124904] Published Wed Dec 24, 2025

Author(s): M. Lebon, Y. Jaunet, J. Sebilleau, and C. Colin

Growth of bubbles nucleated on a wall appear in various industrial applications (gas/liquid contactors, evaporators, hydrogen production), in which their detachment radius is an important parameter for performance optimization. Thanks to gas injection experiments in a shear flow, a force balance model for predicting the detachment radius is built using the relevant forms of the forces extracted from recent literature. A new detachment criterion, based on a maximum advancing contact, allows to determine the receding contact angle and detachment radius with good agreement for both hydrophilic and hydrophobic surfaces.

[Phys. Rev. Fluids 10, 123603] Published Thu Dec 18, 2025

Author(s): Rongfu Guo and Yantao Yang

Basal ice melting under shear flow is a key process in polar and lacustrine environments, where it is influenced by both external forcing and water’s nonlinear equation of state. While previous studies have examined buoyancy-driven convection and shear separately, their interplay with density inversion remains poorly understood. By using direct numerical simulations, we reveal distinct flow regimes and interface morphologies controlled by the inversion stability ratio and effective Richardson number, providing scaling laws for heat transport and a theoretical framework for regime transitions.

[Phys. Rev. Fluids 10, 123502] Published Wed Dec 17, 2025

Author(s): R. Benhammadi, A. De Wit, and J. J. Hidalgo

We investigate the impact of permeability heterogeneity on a bimolecular A + B → C reaction that creates a nonmonotonic fluid density profile which can trigger or suppress convective instabilities. The intensity and structure of heterogeneity control how mixing and reaction scale. We find opposing trends for the mixing of reactants and the reaction depending on the media stratification and the density profile. In horizontally stratified media, reaction is hindered by heterogeneity, while in vertically stratified ones it favors reaction. A similar reaction-favoring behavior is also observed for anisotropic multi-Gaussian log-permeability fields.

[Phys. Rev. Fluids 10, 123501] Published Mon Dec 15, 2025

Author(s): Leon L. Ogorodnikov and Sergey S. Vergeles

The pair correlation function of the velocity field is calculated analytically in a rotating three-dimensional coherent turbulent vortex at distances much larger than the scale of wave forcing and below the vortex size. The function demonstrates anisotropic behavior caused by the relatively large shear flow produced by differential rotation in the vortex. The diagonal elements decrease logarithmically with distance in the streamwise direction, and power-like in radial and vertical directions, that manifest upscale energy transfer. The radial-azimuthal component, which turns into the Reynolds stress for zero distance, is short-correlated and is determined by the forcing correlation function.

[Phys. Rev. Fluids 10, 124702] Published Mon Dec 15, 2025

Author(s): Yifeng Yang and Guoxiong Wu

When surface gravity waves propagate through the Marginal Ice Zone, they interact with numerous floating ice floes and affect the evolution of the polar environment. This work develops a method capable of modeling wave interaction with large arrays of arbitrarily shaped ice floes, which remains highly efficient even when the number of floes becomes exceedingly large. The results show how floe geometry and spatial arrangement influence hydrodynamic forces and scattered wave energy, offering new physical insights into realistic wave–ice interactions.

[Phys. Rev. Fluids 10, 124804] Published Fri Dec 12, 2025

Author(s): Yuhang Zeng, Yan Wang, and Shitang Ke

Numerical simulations of gas-liquid-solid (GLS) interactions play a significant role in many essential areas; however, several challenges related to boundary conditions and mass conservation remain. We present a GLS contact condition-enforced immersed boundary method for simulating multiphase flow problems with curved and moving boundaries. This method has been validated by simulating many challenging GLS problems, indicating that it can accurately enforce Dirichlet and Neumann boundary conditions and efficiently restrain nonphysical liquid/mass penetrations near the solid surfaces. The present method is also applied to more complex GLS problems at large density ratios O(103).

[Phys. Rev. Fluids 10, 124903] Published Fri Dec 12, 2025

Author(s): Yiqian Xu, Kai Mu, Ran Qiao, Chengxi Zhao, and Ting Si

Viscoelastic swirling jets hold significant potential for engineering applications, such as atomizers and combustors. This study carries out theoretical analysis and numerical simulations to investigate the role of elasticity in the instability of swirling jets. It is found that the elastic force could suppress jet instability. However, the suppressing effect is weakened as elasticity gradually increases, thereby enhancing the influence of centrifugal force. This results in modes with the higher azimuthal wavenumbers dominating the jet breakup.

[Phys. Rev. Fluids 10, 124002] Published Thu Dec 11, 2025

Author(s): Francesca Pelusi, Andrea Scagliarini, Mauro Sbragaglia, Massimo Bernaschi, and Roberto Benzi

Understanding how emulsions transport heat under buoyancy forcing is essential in many natural and industrial flows, yet the role of interfacial physics remains poorly explored. Using mesoscale lattice Boltzmann simulations, we compare stabilized and non-stabilized liquid–liquid dispersions in Rayleigh–Bénard convection. While their global heat transfer is similar, stabilized emulsions sustain stronger small-scale heat-flux fluctuations, revealing how interfacial stabilization reshapes convective dynamics at the droplet scale.

[Phys. Rev. Fluids 10, 124305] Published Thu Dec 11, 2025

Author(s): Xiaoyue Zhang, Jin Zhang, and Le Fang

Compressible turbulence exhibits complex mechanisms of energy exchange between kinetic and internal modes, yet their dependence on Mach number remains poorly understood. This work investigates two-dimensional compressible Taylor–Green vortex flows and reveals how Mach number governs the pathway of internal-kinetic energy transfer. We identify three stages of energy evolution and derive an analytical model that predicts the initial growth of dilatational kinetic energy. The results provide new insight into compressible-flow energy exchange and inform future turbulence modeling strategies.

[Phys. Rev. Fluids 10, 123401] Published Wed Dec 10, 2025

Author(s): Haoqi Hu, Wenli Chen, Hui Li, and Donglai Gao

Dense suspensions of finite-size particles exhibit strongly heterogeneous modulation of wall-bounded turbulence. Using interface-resolved Direct Numerical Simulations over a wide range of particle inertia, we show that low-inertia particles homogenize near-wall flow topology and restore a symmetric tear-drop structure in the Q–R plane, whereas high-inertia particles generate asymmetric wake-driven topology, suppress Reynolds stresses, and reorganize the momentum and energy budgets. These results establish a clear physical link between particle-migration-induced flow topology and the regional modulation of turbulence in dense suspensions.

[Phys. Rev. Fluids 10, 124304] Published Tue Dec 09, 2025

Author(s): Maziyar Hassanpour, Robert J. Martinuzzi, and Ugo Piomelli

In turbomachinery and aerodynamics, wake-induced transition can trigger turbulence in boundary layers, yet how wake-separated boundary layer interactions drive transitions is not well understood. We use direct numerical simulations to reveal a hybrid transition pathway — a fusion of classical separated boundary layer instability and wake-driven bypass transition — in boundary layers at moderate gap ratios. Unlike abrupt classical transitions, this process unfolds in distinct stages — linear amplification, nonlinear saturation, and turbulent breakdown — driven by coherent Λ-vortices synchronized with the wake. Our findings offer new insights for transition control in engineering systems.

[Phys. Rev. Fluids 10, 124604] Published Tue Dec 09, 2025

Author(s): Çayan Demirkır, Rui Yang, Aleksandr Bashkatov, Vatsal Sanjay, Detlef Lohse, and Dominik Krug

Early bubble release is vital in electrochemical and boiling systems. Coalescence can trigger bubble departure, but it can also leave bubbles pinned to the electrode surface. By observing the contact-line dynamics and quantifying adhesion and dissipation energies, this work identifies the threshold conditions governing this transition. The developed general energy-balance framework predicts bubble detachment in agreement with available experimental and numerical data.

[Phys. Rev. Fluids 10, 123602] Published Mon Dec 08, 2025

Author(s): Vitor H. C. Cunha, Øivind Wilhelmsen, Carlos Alberto Dorao, and Maria Fernandino

Understanding how intermolecular forces govern nanoscale wetting and phase change requires tools that can link molecular and continuum scales. This work develops a continuum framework that integrates non-local solid-fluid interactions into the Navier-Stokes-Korteweg model, enabling the study of adsorption and thin film dynamics with thermodynamic consistency from the continuum level. By incorporating these interactions directly into the free energy, the model captures near-wall density reorganization and thin film stabilization during phase change, thus providing a consistent framework for examining nanoscale interfacial dynamics while maintaining a clear connection to molecular-level physics.

[Phys. Rev. Fluids 10, 124001] Published Mon Dec 08, 2025

Author(s): Marine Aulnette, Noa Burshtein, Arash Alizad Banaei, Luca Brandt, Simon J. Haward, Amy Q. Shen, Blaise Delmotte, and Anke Lindner

This study explores the transport of microparticles in a three-dimensional stationary vortex generated in a microfluidic cross-slot geometry. Experiments and numerical simulations show that, when increasing particle diameter, particles are progressively excluded from the vortex core. Initially, small particles follow a Burgers vortex-like self-similar motion, but for larger particle diameters, deviations from this trend emerge due to fluid inertia and finite-size effects.

[Phys. Rev. Fluids 10, 124201] Published Mon Dec 08, 2025

Author(s): Daphné Lemasquerier

Turbulent zonal (east–west) jets are ubiquitous in atmospheres, oceans, and planetary interiors. Predicting their long-term nonlinear equilibration is challenging due to complex feedback effects with the underlying turbulence and waves. We address this by deriving a nonlocal closure model that parameterizes Rossby waves and their interaction with large-scale jets. Our new quasilinear model, based on a WKB expansion of the wave field, is the first purely zonal closure to naturally produce zonal jets separated by a Rhines scale. It also reproduces a transition between locally driven and globally driven jets observed in laboratory experiments.

[Phys. Rev. Fluids 10, 124802] Published Mon Dec 08, 2025

Author(s): Julie Deleuze, Ilias Sibgatullin, Philippe Odier, and Sylvain Joubaud

For a stratified fluid in a closed geometry, high amplitude internal waves can be generated by forcing global modes of the domain. These waves can then destabilize through triadic resonant instability (TRI), generating secondary waves. This experimental study, together with an interpretation based on a weakly nonlinear analysis, shows that the combination of box resonance conditions and nonlinear resonance conditions governs the nature of the secondary waves, causing in some cases a significant deviation from the internal waves dispersion relation and in general complex nonlinear interaction dynamics, with multiple pairs of secondary waves appearing dynamically.

[Phys. Rev. Fluids 10, 124803] Published Mon Dec 08, 2025

Author(s): B. Mohammadikalakoo, M. Kotsonis, and N. A. K. Doan

This work presents a real-time, model-free control framework that utilizes single-step deep reinforcement learning to suppress Tollmien-Schlichting waves in a two-dimensional boundary layer. By learning an opposition-control strategy directly from sensor feedback, the controller outperforms a classical adaptive Filtered-x Least Mean Square (FXLMS) approach in both effectiveness and robustness. The results demonstrate a compact and experimentally feasible AI-based solution for real-time control of convective instabilities.

[Phys. Rev. Fluids 10, 124902] Published Mon Dec 08, 2025

Author(s): Guanghang Wang, Jingzhu Wang, Xiangyan Chen, Jianlin Huang, Guangyi Song, Qingyun Zeng, and Yiwei Wang

As a bubble oscillates close to a water surface, a new phenomenon of partial ventilation which the bubble’s exposure to the surrounding air is observed induced by the Rayleigh-Taylor instability penetrating the bubble wall. Depending on the exposure, three distinct types of bubble behaviors with decreasing dimensionless stand-off distance are summarized: (i) nonventilation; (ii) partial ventilation; and (iii) complete ventilation. The boundaries for ventilation time and stand-off distance are obtained by solving the analytical model comprising a small-amplitude model and a bubble-oscillation model, which agrees well with the experimental observations and numerical results.

[Phys. Rev. Fluids 10, 123601] Published Fri Dec 05, 2025

Author(s): Cem Bingol, Matias Duran-Matute, Eckart Meiburg, and Herman J. H. Clercx

The paper presents a study of the evolution of two-dimensional gravity currents, propagating against constant and pulsating counter flow. The effect of mean and oscillatory velocity amplitude on the gravity current evolution, the onset of interfacial shear instabilities such as Kelvin-Helmholtz billows, unstable near-bed density stratification, and the resulting density redistribution is addressed. Two non-hydrostatic processes, shear-driven Kelvin-Helmholtz billows and Rayleigh-Taylor-like overturning induced by differential advection, enhance vertical mixing and horizontal transport of dense fluid within the gravity current and are expected to affect salt intrusion in estuaries.

[Phys. Rev. Fluids 10, 123801] Published Thu Dec 04, 2025