Latest papers in fluid mechanics

Author(s): Xiaoyu Wu and Xian Wang

In this work, an improved Allen-Cahn-based phase-field lattice Boltzmann model is presented which is applicable to heat transfer in two-phase flow involving evaporation. The vapor concentration at the liquid-vapor interface serves as the driving force for vaporization. In our improved model, four di…

[Phys. Rev. E 112, 035102] Published Tue Sep 02, 2025

Author(s): Zhaowu Lin, Yuan Wang, Yufeng Quan, Zhaosheng Yu, Tong Gao, and Sheng Chen

The dynamics of microswimmers’ undulatory swimming near a wall in lyotropic liquid crystal polymers is investigated. Using asymptotic analysis and numerical study, we observe that the infinitely long sheet exhibits orientation-dependent behaviors and speeds up as it approaches the wall, accompanied by a notable increase in swimming efficiency. For the stiff finite-length swimmers, they would reorient themselves and be trapped when close enough to the wall, due to a net hydrodynamic torque induced by the asymmetric distribution of the flow field.

[Phys. Rev. Fluids 10, 083302] Published Thu Aug 28, 2025

Author(s): Garima Singh, Chhavi Shukla, and Naveen Tiwari

Stability of a liquid film containing colloidal particles flowing along the exterior of a vertical cylinder due to gravity is studied. The effect of colloidal concentration on diffusion coefficients, bulk viscosity, and surface tension is considered. The Marangoni stress at the interface stabilizes the curvature-driven instability at moderate Marangoni numbers, but introduces another unstable mode driven by surfactant at larger values. The pattern for the curvature mode indicates in-phase waves for film thickness and surface concentration, while a phase-lag is observed between the two waves for the surfactant mode.

[Phys. Rev. Fluids 10, 084005] Published Thu Aug 28, 2025

Author(s): Sreethin Sreedharan Kallyadan and Priyanka Shukla

Four interacting point vortices can form rigidly moving patterns called relative equilibria, yet a complete understanding of the possible geometrical arrangements has been elusive. Using a parametric formulation and configuration matrices, we mapped the locations of the fourth vortex that form relative equilibria for a fixed triangular arrangement of the first three vortices. The results reveal bounded and unbounded continua of vortex positions, uncovering families of relative equilibria and rich bifurcation structures in the configuration space.

[Phys. Rev. Fluids 10, 084708] Published Thu Aug 28, 2025

Author(s): Nicolas Lanchon, Samuel Boury, and Pierre-Philippe Cortet

Understanding internal wave turbulence in stratified fluids could yield improved parameterizations of the fine scales in global oceanic models. As analytical works lead to diverse predictions, the observation of a developed internal wave turbulence in laboratory experiments constitutes a major milestone to achieve. In this article, we present observations of internal wave turbulence, performed in a large-scale, three-dimensional facility, allowing access to unprecedentedly clear power laws for the energy spectra. While most of our results are in line with the phenomenology of wave turbulence, it remains to be explored whether the energy spectra we report can be explained in this framework.

[Phys. Rev. Fluids 10, 084804] Published Thu Aug 28, 2025

Author(s): Van Luc Nguyen, Dinh Thang Nguyen, Thi Dieu Thuy Phan, and Long Hoang Duong

When a vortex ring collides obliquely with a vortex tube at a Reynolds number of 12,000, a series of vortex structures can form, with the onset of turbulence set by their initial circulation ratio. Weaker vortices often wrap around stronger ones, causing deformation, twisting, and breakdown of large-scale structures into smaller scales. Vortex reconnection may produce more stable configurations; however, changes in vortex topology can trigger secondary reconnections, generating even more twisted structures. As these vortices become unstable, they create numerous small-scale structures, ultimately leading to fully developed turbulence with an energy spectrum following Kolmogorov’s −5/3 law.

[Phys. Rev. Fluids 10, 084707] Published Wed Aug 27, 2025

Author(s): Rafael L. Sterza, Leandro F. Souza, Marcio T. Mendonca, Analice C. Brandi, and André V. G. Cavalieri

The stability of viscoelastic jets is essential for industrial processes like printing and coating, but the choice of fluid model can yield vastly different predictions. This study investigates how the popular Oldroyd-B and Giesekus models affect the onset of convective instability, where disturbances grow downstream, versus absolute instability, where they grow locally. We demonstrate a key trade-off: Giesekus jets are more convectively unstable, while Oldroyd-B jets are more prone to absolute instability. These findings clarify how different fluid properties govern distinct instability pathways, guiding better process control.

[Phys. Rev. Fluids 10, 083902] Published Tue Aug 26, 2025

Author(s): Ehud Yariv

In 1922, Jeffery solved the problem of cylinder-pair counterrotation in a viscous fluid and found that it is impossible to satisfy velocity decay at infinity. Following recent interest in this so-called ‘’Jeffery paradox,’’ the present paper sheds some light on the counterrotation and corotation problems in the limit where the separation between the cylinders is vanishingly small.

[Phys. Rev. Fluids 10, 084101] Published Tue Aug 26, 2025

Author(s): Ying Xiong, Yang Zhang, Xiaolei Li, and Lingling Xie

The high-order surface quasigeostrophic (SQG+1) turbulence is investigated numerically in this work with a focus on how lateral divergence modifies cross-scale energy transfers. The SQG+1 model extends the classic SQG model by incorporating a velocity correction that introduces controlled divergence…

[Phys. Rev. Fluids 10, 084604] Published Tue Aug 26, 2025

Author(s): Chiara Calascibetta, Luca Biferale, Fabio Bonaccorso, Massimo Cencini, and Alexei A. Mailybaev

The statistical behavior of a scalar passively advected by a Navier-Stokes flow resulting from a two-dimensional turbulent inverse energy cascade is strongly intermittent, displaying anomalous multiscaling, which violates Kolmogorov’s self-similarity predictions. Recently, the concept of hidden symmetry (HS) has been introduced to define a new set of dynamically rescaled (projected) variables for which scale invariance is restored and allowing to calculate from the projected equation of motion the anomalous scaling of the structure functions. Hidden symmetry has been validated numerically in the context of the shell models. In this work we validate HS for the case of the passive scalar.

[Phys. Rev. Fluids 10, 084605] Published Tue Aug 26, 2025

Author(s): Chung-Hao Chen, Zong-Rou Jiang, and Tzay-Ming Hong

The process of producing a liquid column is common in daily life and industrial applications, such as walking through a puddle and roller printing. While governed by the Navier-Stokes equation, its dynamics are often studied by numerical means, which hinders a full understanding of the rich mixture …

[Phys. Rev. E 112, 025105] Published Mon Aug 25, 2025

Author(s): Zhiwei Song and Zijing Ding

This study develops a weighted-residual model for Oldroyd-B films on slippery substrates at moderate Reynolds number and large slippery length. Linear stability analysis reveals that wall slip promotes perturbation growth rates, increases cut-off wave numbers, and accelerates long-wave propagation s…

[Phys. Rev. E 112, 025106] Published Mon Aug 25, 2025

Author(s): Yuke Li and Victor Steinberg

Discovered stochastic resonance (SR) in viscoelastic inertialess channel flow at a fixed location far from inlet has Wi as control parameter (CP), the ratio of elastic stress to its relaxation. By tracking SR downstream along channel locations at Wi>Wic, we find that a SR existence range first broadens in Wi values and then remains constant until the outlet, with perturbation intensity as the second CP defining the range of SR appearance. SR existence should satisfy three conditions: chaotic streamwise and flat, weak intensity spanwise power spectra with extremely small elastic wave intensity. Thus, SR plays the key role in stochastic routes to promote sustained chaotic flow at Wi>Wic.

[Phys. Rev. Fluids 10, L081901] Published Mon Aug 25, 2025

Author(s): Tanumoy Dhar, Michael J. Shelley, and David Saintillan

We investigate the stability of two configurations: a passive viscous Newtonian droplet immersed in an active nematic liquid crystal, and an active nematic droplet surrounded by a passive layer, both under circular confinement. Our results reveal how capillary, active, elastic, and viscous stresses interact to govern droplet dynamics. These findings may inform our understanding of diverse biological systems featuring interfaces between active and passive fluids, from droplets in bacterial suspensions to subcellular compartments within the cytoplasm and cell nucleus.

[Phys. Rev. Fluids 10, 083103] Published Thu Aug 21, 2025

Author(s): Yuejia Zhang, Nicholas J. Moore, and Jinzi Mac Huang

Heavy fluid sinks while light fluid rises – these are the very basics of convection. Here we derive a set of reaction-diffusion equations from the governing dynamics of convection, whose solutions reveal complex flows that display both order and chaos. By tuning the strength of buoyancy (Rayleigh number), a series of transitions between conducting, circulating, and reversing flows appears, leading to an enhanced heat transfer (Nusselt number). This model also reveals a ¼ power-law scaling between the Nusselt and Rayleigh numbers that is verified by both numerical simulations and asymptotic analysis, bringing us one step closer towards understanding the complex physics of convective heat transfer.

[Phys. Rev. Fluids 10, 083501] Published Thu Aug 21, 2025

Author(s): Zhe Feng

This study provides a plausible explanation for the longstanding discrepancy between experiments and simulations of electroconvective flows by systematically incorporating Navier-slip boundary conditions. It demonstrates that partial slip can significantly lower both linear and nonlinear instability thresholds and enhances electric transport efficiency. A previously unreported transition from convective to zonal flows is also uncovered, offering a physical mechanism for the saturation of electric transport observed in experiments. These findings establish a predictive framework linking boundary slip to the stability and turbulent transport characteristics of electroconvective flows.

[Phys. Rev. Fluids 10, 083701] Published Thu Aug 21, 2025

Author(s): Anubhav Dubey, Constantin Habes, Holger Marschall, and Sakir Amiroudine

Binary fluids with miscibility gap exhibit property variation in response to a stimuli, making them useful for applications like targeted drug delivery, protein extraction, and others. We present a novel phase-field approach to track the continuous evolution of such fluid pairs from initially immiscible/partially miscible state to miscible state with a tunable miscibility framework. The model is used to investigate classical single mode Rayleigh-Taylor instability. Three qualitatively distinct growth patterns of the imposed perturbation are found based on the Atwood and Weber numbers. A secondary instability of Kelvin-Helmholtz rolls is found to be dependent on system temperature.

[Phys. Rev. Fluids 10, 084004] Published Thu Aug 21, 2025

Author(s): Gabriel Marchetti and Pablo D. Mininni

Three dimensional rotating turbulent flows can sometimes transfer energy from the injection scale to the largest scale available in the domain, generating large coherent structures in the process. For intermediate values of the Rossby number, however, a flux–loop mechanism can be achieved, in which the energy transferred upscale is arrested at a scale smaller than the domain size. This mechanism also produces coherent structures similar to the vortex crystals usually found in many physical systems. In this work we study these structures via direct numerical simulations, focusing on their evolution and morphology, and we identify their key controlling parameters.

[Phys. Rev. Fluids 10, 084603] Published Thu Aug 21, 2025

Author(s): Ranit Mukherjee, Zih-Yin Chen, Xiang Cheng, and Sungyon Lee

Particle rafts — fluid-fluid interfaces covered with particles — form wrinkles and folds when compressed, like a crumpled piece of paper. Nevertheless, composed of discrete particles, rafts under compression can also fail by expelling single particles, which cannot be explained by existing continuum models. We develop a composite model that incorporates the contact line dynamics of individual particles to fully describe both the elastic and granular responses of the compressed particle rafts. By using this new model framework, we also demonstrate the control of raft behaviors by tuning the physicochemical properties of individual particles.

[Phys. Rev. Fluids 10, 084003] Published Wed Aug 20, 2025

Author(s): Harshal S. Raut, Jung-Hee Seo, and Rajat Mittal

Wave-powered propulsion using flapping foils is a relatively new idea with great potential, but the performance of these systems depends strongly on foil geometry and pitch control. Using high-fidelity fluid–structure simulations, this study examines pitch-limiting strategies and foil shapes that can maximize thrust across a range of sea states. A simple pitch angle-limiter offers performance benefits especially in low amplitude waves, while a thin elliptical foil outperforms other foil shapes. These results provide practical design guidelines for efficient wave-powered flapping foil propulsion systems.

[Phys. Rev. Fluids 10, 084705] Published Tue Aug 19, 2025