New Papers in Fluid Mechanics

Author(s): Coen I. Verschuur, Alexandros T. Oratis, Vatsal Sanjay, and Jacco H. Snoeijer

The pinch-off of drops and bubbles from a needle are classic examples of hydrodynamic singularities, in which a fluid body splits into two. While even small amounts of polymers strongly delay drop breakup by forming long liquid threads, recent experiments show that bubble pinch-off remains largely unaffected. In this article we demonstrate that polymer stretching cannot compete with the violent inertial collapse governing bubble pinch-off. Only for sufficiently high polymer concentrations and small needle sizes can viscoelastic effects delay breakup, resulting in the formation of air cavities.

[Phys. Rev. Fluids 11, 073302] Published Mon Jul 13, 2026

Author(s): M. Kharbedia, H. Franca, H. K. Schubert, D. J. Engels, M. Jalaal, and O. O. Versolato

We experimentally and numerically investigate nanosecond laser-induced jetting dynamics of a free-falling micro-sized liquid tin droplet. Following laser impact, the droplet rapidly expands and retracts, leading to the formation of a high-speed axial jet. A specific combination of laser-induced pressure and its angular distribution on the droplet surface drives cavity formation, ultimately giving rise to a singular jet. We reveal the underlying mechanism and construct a phase diagram explaining jet emergence as the result of a subtle interplay between droplet curvature during retraction and radial flow.

[Phys. Rev. Fluids 11, 073602] Published Mon Jul 13, 2026

Author(s): Nishant Nair, Clément de Loubens, Romain Lhermerout, Benjamin Cross, and Hugues Bodiguel

Charge transfer between particles is believed to strongly influence the mechanical properties of many suspensions, yet it remains difficult to observe directly. We demonstrate that biopolymer microcapsules exhibit a unique bouncing dynamics under an alternating electric field that is consistent with repeated charge transfer during contact. These findings identify Coulombic interactions as the origin of the attractive forces responsible for the fragile gel behavior and yield stress previously observed in suspensions of these microcapsules.

[Phys. Rev. Fluids 11, 073701] Published Mon Jul 13, 2026

Author(s): Marc Prat, Pierluigi Arnelli, Michel Quintard, and Joel Pauchet

Controlling the distribution of colloidal particles during drying of a thin porous medium is of importance for various technological applications. The liquid phase distribution during drying in a thin system is strongly affected by two effects, referred to as the edge and breakthrough effects. The impact on the colloid distribution during drying of both effects is studied. Simulations indicate markedly more uniform colloid spatial distributions as the result of both effects compared to predictions based on the standard model ignoring these effects.

[Phys. Rev. Fluids 11, 074301] Published Mon Jul 13, 2026

Author(s): Karuna Pathirannehelage Pasan Sanjeeva and Yoshiyuki Tsuji

Particle-vortex interactions in quantum turbulence are essential for interpreting the results from particle-laden experiments in superfluid He II thermal counterflow. In this experimental investigation, we extracted and analyzed trapping and de-trapping processes of small particles on quantum vortex lines. Our results show an asymmetry between the two processes, indicating that they are governed by distinct physical mechanisms, and suggest that they exhibit self-similar features across small time lags. These results deepen our understanding of trapping and de-trapping processes of particles, and the dynamics of particle motion in turbulent thermal counterflow under two-fluid interactions.

[Phys. Rev. Fluids 11, 074602] Published Mon Jul 13, 2026

Author(s): Rui Tang, Ke Zhou, Jifu Tan, and Samuel J. Grauer

Experimental studies of fluid–structure interactions (FSI) rarely capture dense, simultaneous measurements of both the fluid and solid phases, which limits analysis of the coupled dynamics. We present a physics-informed data assimilation framework that reconstructs both the flow and structure from sparse, off-body particle tracks, i.e., without requiring a constitutive model or direct observations of the structure. The method accurately recovers coupled dynamics in 2D and 3D benchmarks, allowing for quantitative measurements of FSI from limited data.

[Phys. Rev. Fluids 11, 074901] Published Mon Jul 13, 2026

Author(s): Sneha Krishnan and Rickmoy Samanta

Active proteins and membrane-bound motors exert force dipole flows along fluid interfaces and lipid bilayers. We develop a Hamiltonian framework for the interactions of pusher and puller dipoles embedded in an incompressible two-dimensional membrane supported by a shallow viscous subphase. Beginning…

[Phys. Rev. E 114, 015102] Published Mon Jul 13, 2026

Author(s): Omid Tavakkoli, Dick Bedeaux, Signe Kjelstrup, Steffen Berg, Marcel Moura, Ying Da Wang, Peyman Mostaghimi, and Ryan T. Armstrong

We introduce a nonequilibrium thermodynamic (NET) framework for immiscible two-phase flow in porous media, in which the total flux of both phases is driven by the gradient of an effective pressure. We show that the classical two-phase Darcy formulation emerges as a projected limit of the full linear…

[Phys. Rev. E 114, 015103] Published Mon Jul 13, 2026

Author(s): Julián Amette Estrada, Alexandros Alexakis, Marc E. Brachet, and Pablo D. Mininni

Ordered vortex lattices, familiar from quantum systems like Bose-Einstein condensates and type II superconductors, have emerged in classical rotating turbulence, but the mechanisms controlling their stability remain elusive. By embedding ideal, defect-free triangular arrays into three-dimensional turbulent flows, we map the region of parameter space where these structures survive and establish their characteristics. Their lifetimes obey a memoryless random process whose mean depends sensitively on the Rossby number and energetic balance, with optimally tuned dissipation yielding long-lived states whose statistics resemble those of critical systems.

[Phys. Rev. Fluids 11, 074401] Published Fri Jul 10, 2026

Author(s): Ping-Fan Yang, Haitao Xu, and Alain Pumir

The intense fluctuations of the rate of energy dissipation, an essential aspect of intermittency, are of constant interest in turbulence research. Measuring the energy dissipation, however, is extremely challenging: Most of our knowledge comes from hot-wire measurements of the derivative of the streamwise velocity component, which is generally regarded as a surrogate of the energy dissipation. Here we show that the moments of the energy dissipation cannot reduce to those of its surrogate, as a consequence of a fundamental property of the rate of strain tensor in turbulence. However, the predictions based on assuming a simplified strain rate tensor are accurate to within a few percent.

[Phys. Rev. Fluids 11, 074601] Published Fri Jul 10, 2026

Author(s): Yoshiki Hiruta

Subcritical transition to turbulence, in which the laminar state is linearly stable yet finite-amplitude perturbations develop into turbulence, is ubiquitous but predicting it from the structure of the governing equations remains difficult. We demonstrate such a framework using a shell model of turb…

[Phys. Rev. E 114, L013101] Published Wed Jul 08, 2026

Author(s): Rabia Sonmez, Robert A. Handler, David B. Goldstein, Anton Burtsev, Ryan Kelly, and Saikishan Suryanarayanan

We show that the interaction of a vortex pair with a localized polymeric fluid layer can generate secondary and tertiary vortices through polymer stress gradients. Numerical simulations reveal that elastic stresses significantly modify vorticity production and energy transfer, leading to flow behaviors not observed in Newtonian fluids. The image shows the vorticity field during the interaction.

[Phys. Rev. Fluids 11, 073301] Published Mon Jul 06, 2026

Author(s): Paolo Botticini, Davide Picchi, Santanu Sinha, and Alex Hansen

We characterize the nonlinear pressure drop–flow rate relation of elongated bubble trains in capillary tubes by incorporating thin-film hydrodynamics at low capillary numbers. We show that pore-scale statistical heterogeneity in capillary bundles induces systematic deviations from the single-phase limit, controlled by both the pore-size distribution and flow parameters. We identify a crossover between sublinear regimes with exponents ranging from 2/3 to 1, connecting the Bretherton and Darcy limits and in qualitative agreement with values reported for immiscible two-phase flow in porous media.

[Phys. Rev. Fluids 11, 073601] Published Mon Jul 06, 2026

Author(s): Linsheng Zhang (张林生), Weixing Zhou (周伟星), and Robert J. Poole

We revisit the classical homogeneous shear assumption in cone-and-plate rheometry over a slip boundary condition, and resolve inconsistencies between two slip boundary formulations. Our results show that a fixed slip-length model induces radial shear-rate non-uniformity, whereas a constant wall-stress formulation restores homogeneous shear via a radius-dependent slip length. Extending our work to shear-thinning Carreau fluids, we demonstrate a strong shear-rate dependence of drag reduction and effective slip length. Despite distinct local flow structures, both models yield consistent area-averaged slip from torque measurements, providing a unified framework for slip quantification.

[Phys. Rev. Fluids 11, 074001] Published Mon Jul 06, 2026

Author(s): George Lucas S. Torres, Ashok Gopalarathnam, and Flávio D. Marques

Unsteady thin-airfoil theory is a straightforward reduced-order framework for arbitrary airfoil motions and geometries. However, an inconsistency appears when recovering classical unsteady problems: Glauert’s bound-vorticity expansion is not uniformly convergent at the trailing edge in unsteady motion. Revisiting Wagner’s problem through the unsteady Kutta condition, this work derives a recurrence for the bound-vorticity coefficients and builds a uniformly convergent bound vortex-sheet formulation with a discrete-vortex equivalent. With few terms, the method ensures bound-wake continuity, zero trailing-edge loading, and smooth transient predictions for Wagner’s indicial problem

[Phys. Rev. Fluids 11, 074701] Published Mon Jul 06, 2026

Author(s): Kai Tian, Tongtong Zhu, Xiaoyu Xu, Zhaodong Ding, Jifeng Cui, and Chundong Xue

This study investigates the evolution mechanism of elastic instability in a bilateral double-cavity channel through numerical simulations and microfluidic experiments. Depending on the Weissenberg number (Wi), the flow is categorized into three regimes: stable symmetric vortex structures at low Wi (…

[Phys. Rev. E 114, 015101] Published Wed Jul 01, 2026

Author(s): Nayoung Kim, Felix Schindler, Sylvie Su, Sven Eckert, and Tobias Vogt

Turbulent thermal convection often organizes into large-scale flow structures that control heat and momentum transport, yet their dynamics in very wide systems remain largely unexplored. Using a liquid-metal Rayleigh–Bénard convection experiment with an extreme aspect ratio of 25, we demonstrate that jump rope vortex dynamics persist even within turbulent convective superstructures. The observed oscillatory behavior follows the same scaling laws previously identified in much smaller systems, indicating that jump rope vortex dynamics are not confined to specific geometries but remain relevant even in spatially extended convection at extreme aspect ratios.

[Phys. Rev. Fluids 11, 063503] Published Tue Jun 30, 2026

Author(s): Mohd. Hanzla, Christopher Ruhl, and Arindam Banerjee

Active grids are widely used to generate turbulence, yet their near-grid region remains poorly understood. We show that global blockage is a key parameter governing near-grid turbulence statistics, driving qualitatively different behavior when grid configuration changes, in contrast to trends observed further downstream. We further reveal that forcing signatures persist strongly at large scales but decay toward dissipative scales, marking a transition from forcing-dominated to more universal turbulence.

[Phys. Rev. Fluids 11, 064617] Published Tue Jun 30, 2026

Author(s): Jinbo Cheng, Wang Han, Yihao Tang, and Lijun Yang

Soot formation in aero-engine combustors is influenced by coherent structures of confined turbulent swirling flows. This work combines large-eddy simulation with state-of-the-art soot models and spectral Proper Orthogonal Decomposition (POD) to identify flow dynamics directly from raw transient data. The results reveal a scale-dependent response: Polycyclic aromatic hydrocarbons (PAH) are mainly affected by high-frequency processing vortex core motion, whereas soot is governed by low-frequency dynamics. Dilution jets weaken high-frequency flow motions and modify the coupling among coherent structures, gas-phase precursors, and soot evolution.

[Phys. Rev. Fluids 11, 063201] Published Mon Jun 29, 2026

Author(s): S. K. Bohling, S. S. Tanikella, J. P. Raimondi, N. D. Jones, and E. Dressaire

Hair-covered appendages serve a variety of purposes in Nature, from chemical sensing to drag generation. To understand how these natural systems control flow, we study how confinement, porosity, and Reynolds number affect flow through and around a finite array of cylinders, using a combination of experiments and numerical simulations. Our results show that the confinement focuses the flow in the array and shifts the domains of existence of the flow regimes. We perform a theoretical analysis based on Sampson flows through rectangular slits to predict the flow rate through the array. The model is quantitatively consistent with the numerical results.

[Phys. Rev. Fluids 11, 064104] Published Mon Jun 29, 2026