New Papers in Fluid Mechanics

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

Author(s): Marcel M. Louis, Lekwetje Maureen Ramaube, Sonya T. Smith, and Howard A. Stone

The influence of a temperature-dependent viscosity and wall slip are considered for high-Reynolds-number flow over a heated flat plate. In the limit of a small dimensionless slip length, which serves as a perturbation parameter, similarity solutions are developed. The results are used to study the combined effect of temperature-dependent viscosity and wall slip on the coefficients of friction and the Nusselt number. For example, the asymptotic solutions show that the slip contributions to the flow are enhanced by temperature-dependent viscosity.

[Phys. Rev. Fluids 11, 064105] Published Mon Jun 29, 2026

Author(s): Alessandro Chiarini, Rahul K. Singh, and Marco E. Rosti

Polymeric flows exhibit phenomena that sit at odds with our conventional understanding of turbulence. In this work, we show how a characteristic far-from-Kolmogorov self-similarity of polymeric turbulence owes its emergence to a phenomenon possible only in multiphase flows: polymers deplete the fluid energy cascade at a constant rate across scales. This constant loss of flux from fluid to polymers emerges as a second invariant of the turbulent, strongly coupled, fluid-polymer system (in addition to the total constant flux of energy from large to small scales). This invariant loss of flux dictates turbulence statistics in polymeric flows and gives it a distinct universal power-law behavior.

[Phys. Rev. Fluids 11, 064616] Published Mon Jun 29, 2026

Author(s): Zhigang Zhang, ChenXu Zhang, Chi Zhang, Takahito Iida, and Xiangqian Zhu

Water-wave focusing is a significant technology for enhancing wave energy density, which can effectively improve the efficiency of the wave energy converter. To achieve parabolic focusing of water waves using a straight boundary, the space transformation method (STM) was employed to map a parabolic …

[Phys. Rev. E 113, 065110] Published Fri Jun 26, 2026

Author(s): S. E. Kuratov, A. Yu. Mikulin, S. I. Glazyrin, and D. S. Shidlovski

The development of hydrodynamic instabilities may be significantly affected by the presence of suprathermal high-energy particles (HEPs). These effects are particularly pronounced in high-energy-density plasmas. We develop a single-equation diffusion-type turbulence model that describes the turbulen…

[Phys. Rev. E 113, 065111] Published Fri Jun 26, 2026

Author(s): R. Mathis, S. Cazin, J. Methel, F. Charru, J. Magnaudet, F. Moisy, and M. Rabaud

The growth of wind-generated waves may depend on free-stream turbulence, a parameter that is generally neglected in existing models. Here, we investigate this effect experimentally using grid-generated turbulence blowing over a viscous fluid. Our results show that free-stream turbulence enhances the amplitude of three-dimensional wrinkles and lowers the critical wind velocity for the onset of regular two-dimensional waves, while the wrinkle–wave transition remains associated with an approximately constant friction velocity. A qualitative model explains why the observed decrease of the friction velocity with the fetch results in a non-monotonic variation of the wave amplitude.

[Phys. Rev. Fluids 11, 064804] Published Fri Jun 26, 2026