New Papers in Fluid Mechanics

Author(s): Victor Botez, André Giesecke, Caroline Nore, Loïc Cappanera, and Frank Stefani

In preparation for the DRESDYN precession dynamo experiment, we numerically investigate how wall material properties impact the growth of magnetic modes driven by a precessing flow. We identify two oscillating magnetic modes - dipolar and quadrupolar – whose competition explains the drastic changes in dynamo thresholds for different types of boundaries. For given hydrodynamic parameters, these modes are paramount for a comprehensive understanding of all electromagnetic configurations, including the realistic modeling of the upcoming first liquid sodium campaign.

[Phys. Rev. Fluids 11, 083701] Published Fri Aug 14, 2026

Author(s): Sanghasri Mukhopadhyay, Séverine Millet, Bastien Di Pierro, and Asim Mukhopadhyay

Gravity-driven thin films laden with soluble surfactants play a central role in coating technologies and microfluidic systems, where reduced-order models are widely used to predict interfacial dynamics. Some weighted-residual formulations, however, introduce spurious interfacial mass growth, violating total surfactant conservation. We resolve this inconsistency by developing a conservative weighted-residual model that consistently couples wall slip, adsorption-desorption, and the Marangoni effect while rigorously preserving total surfactant mass. The resulting framework provides physically consistent predictions of instability onset, nonlinear wave dynamics, and surfactant transport.

[Phys. Rev. Fluids 11, 084004] Published Fri Aug 14, 2026

Author(s): Wenhao Cheng and Zeng Liu

Wind-driven wave evolution is commonly viewed as a two-stage process: initial wave growth followed by frequency downshift. Here, we reveal a previously unrecognized intermediate stage in the evolution of capillary–gravity waves under wind forcing and dissipation. This stage is characterized by coupled three- and four-wave near-resonant interactions that generate new wave components, broaden the spectrum, and may reduce total wave energy. These findings constitute a major step forward in understanding the evolution of wind waves from small ripples (2.5 cm) to larger-scale waves.

[Phys. Rev. Fluids 11, 084801] Published Fri Aug 14, 2026

Author(s): Írio M. Coutinho, Liam C. Morrow, and Scott W. McCue

Interfacial Hele-Shaw flows often involve fingering instabilities, tip-splitting phenomena and striking pattern formations. This study revisits a simplified model that characterizes the complexity of these fingering patterns and identifies some universal features. We test this model using fully nonlinear numerical simulations and find that it is very effective at predicting near-universal properties of the fingering patterns for one-phase flows with a sufficiently small surface tension parameter. For larger values of this parameter and for two-phase flows, there are discrepancies between the model and our observations, which we explain by studying the morphology of the advancing fingers.

[Phys. Rev. Fluids 11, 084003] Published Thu Aug 13, 2026

Author(s): Haowei Qiu, Adam Jiankang Yang, and Baafour Nyantekyi-Kwakye

Ocean Alkalinity Enhancement (OAE) is a promising marine carbon dioxide removal strategy involving the release of alkaline particles into the ocean. However, its effectiveness depends on how these particles disperse. This study uses high-resolution simulations to show that collective convective instabilities, rather than individual Stokes settling, fundamentally govern particle settling. These instabilities can accelerate vertical particle transport by up to two orders of magnitude, significantly limiting horizontal spread and surface residence time. These fundamental fluid-dynamic constraints provide essential guidance for optimizing future OAE deployments.

[Phys. Rev. Fluids 11, 084503] Published Thu Aug 13, 2026

Author(s): Shreyashri Sarkar and Rishita Das

Small-scale intermittency is conventionally modeled by power laws of higher-order moments, which include both kinematic and turbulence-driven effects. By using Kullback-Leibler divergence relative to a Gaussian random field, we isolate purely turbulence-induced intermittency, which scales logarithmically with the Taylor Reynolds number. This reveals an emergent symmetry between the turbulence intermittency of dissipation rate and enstrophy, showing that enstrophy appears more intermittent for purely kinematic reasons. The work establishes an information-theoretic framework for characterizing the intermittency and uncertainty of small-scale turbulence.

[Phys. Rev. Fluids 11, 084605] Published Thu Aug 13, 2026

Author(s): Xingguang Zhou, Dalin Zhang, Xinyu Li, Wentao Ma, Hongxing Yu, Wenxi Tian, Suizheng Qiu, and Guanghui Su

Mixed convection for heavy liquid metals is still terra incognita in many aspects, because of the complex flow mechanism, strong thermal diffusivity, and optical opacity. Understanding the flow organization is key to turbulence research and practical engineering. We use high-fidelity scale-resolving numerical simulations to explore the unique large-scale longitudinal roller structures in mixed convection, while also considering the low Prandtl number effect of heavy liquid metals. A new physical interpretation for the slope modulation phenomenon of the mean velocity profile is established, which is expected to give new insights into wall function modeling in mixed convection.

[Phys. Rev. Fluids 11, 084606] Published Thu Aug 13, 2026

Author(s): Xiantao Fan, Meet Hemant Parikh, Yi Liu, Xin-Yang Liu, Junyi Guo, Meng Wang, and Jian-Xun Wang

Most studies of turbulent wall pressure reduce its dynamics to wavenumber-frequency spectral descriptions, leaving the instantaneous, spatially evolving pressure field largely inaccessible to experiments and prohibitively expensive simulations. We introduce a probabilistic generative approach that reconstructs full spatiotemporal wall-pressure fields from sparse surface measurements and a low-cost mean-pressure descriptor. Combining patchwise neural representations with latent diffusion, the model adapts to unseen sensor layouts and pressure-gradient regimes without retraining. It recovers coherent structures, temporal evolution, and key turbulence statistics.

[Phys. Rev. Fluids 11, 084607] Published Thu Aug 13, 2026

Author(s): Vikas S. Krishnamurthy and Takashi Sakajo

The stationary equilibria of N point vortices in a rectangular domain with doubly periodic boundary conditions offer a foundational framework for understanding the stationary lattices of coherent vortex structures. In this paper, we obtain new continuous families of these lattices. These solutions a…

[Phys. Rev. E 114, 025105] Published Thu Aug 13, 2026

Author(s): Albert Dai and Yu-Lin Huang

When gravity currents converge inward, such as sea breezes closing in around an island or lake, their collision unfolds very differently from the situation when two gravity currents meet head-on. Using high-resolution three-dimensional simulations, this study reveals, for the first time, how such collisions generate turbulence: vorticity arises primarily through tilting of azimuthal vorticity rather than through the stretching mechanism as seen in planar collisions. The resulting eddy diffusivity data support existing mesoscale-model parameterizations used to represent gravity current collision events in atmospheric and oceanic models.

[Phys. Rev. Fluids 11, 083801] Published Wed Aug 12, 2026

Author(s): Tino Damiani, Matthew Durey, Bauyrzhan K. Primkulov, and John W. M. Bush

A millimetric droplet may walk across the surface of a vibrating liquid bath, self-propelled by its own wave field. This pilot-wave hydrodynamic system has provided the basis for the field of hydrodynamic quantum analogs, the goal of which is to redefine the boundaries between classical and quantum systems. We here deepen our understanding of pilot-wave hydrodynamics through consideration of its energetics, evaluation of the partitioning between droplet and wave energies. Photo credit: Pedro Nachbin.

[Phys. Rev. Fluids 11, 084002] Published Wed Aug 12, 2026

Author(s): D. M. Escala, I. Castaldi, and A. De Wit

Previous theoretical works showed that, in double-diffusion regimes, the onset time and mixing velocity of convective fingers are controlled by a dynamic density jump across stratified layers. Here, we experimentally validate these scalings by analyzing differential diffusion-induced convection in horizontal stratifications within a Hele-Shaw cell. Using a wide range of solute combinations and concentrations, we vary the two key parameters of the problem: the diffusion coefficient and buoyancy ratios. We show that, in both double-diffusive and diffusive-layer-convection regimes, convective dynamics are governed by dynamically generated local adverse density jumps.

[Phys. Rev. Fluids 11, 084502] Published Tue Aug 11, 2026

Author(s): Flavio Tuteri, Sergio Chibbaro, and Alexandros Alexakis

Classical shell models of turbulence fail to reproduce the dual energy–enstrophy cascade of two-dimensional flows because they predict the wrong equilibrium spectra. Introducing a hierarchical spatial organization across scales restores the correct equilibrium scaling and leads to a statistically stationary dual cascade. The resulting model consistently captures both the equilibrium properties and the nonequilibrium cascade dynamics of two-dimensional turbulence.

[Phys. Rev. Fluids 11, 084604] Published Tue Aug 11, 2026

Author(s): Xiangyu Nie and Shengkai Wang

We report direct experimental observations of self-sustaining CH4–air flames rotating along the edge of an unheated circular Hele-Shaw cell, extending beyond previous studies in which such flames were observed only under external heating. Formed under fuel-rich conditions, these flames exhibit stable traveling-wave behavior, with edge velocities exceeding nominal laminar flame speeds and a structure comprising both premixed and diffusion branches. The rotation arises from a balance between local flame speed, flow, and wall heat loss. Parametric studies have identified regimes of single and multiple rotating waves, as well as transitions to ring flames or extinction under extreme conditions.

[Phys. Rev. Fluids 11, 083201] Published Mon Aug 10, 2026

Author(s): Suruj Kalita and Rajaraman Ganesh

We investigate subcritical turbulence in plane Couette flow using a finite-amplitude columnar vortex instead of the conventional Lundbladh-type perturbation. We show that, although the perturbation modifies the turbulent structure, the key characteristics of subcritical turbulence remain unchanged. The figure illustrates the breakdown of the columnar vortex into tripolar and quadrupolar structures in unstratified and stably stratified flows. The columnar vortex breakup provides a new mechanism for streamwise streak formation.

[Phys. Rev. Fluids 11, 083301] Published Mon Aug 10, 2026

Author(s): Pratyush Kumar Mohanty, P. S. D. Surya Phani Tej, Gade Sanjana, and V. Shankar

We revisit the classical hoop-stress mode (HSM) instability in viscoelastic Taylor-Couette flow using the FENE-P model. We show how finite polymer extensibility modifies the onset of the hoop-stress mode for a range of gap width ratios. By systematically comparing linear stability predictions with experiments and direct numerical simulations, we identify where the model succeeds and where its limitations emerge and what are the possible reasons for the discrepancies. We also compare our linear stability results with an augmented Pakdel–McKinley criterion that incorporates finite extensibility and finite gap effects.

[Phys. Rev. Fluids 11, 083302] Published Mon Aug 10, 2026

Author(s): Meng Fan, Antoine Dazin, Gérard Bois, and Francesco Romanò

Low-flow-rate instabilities in vaneless diffusers remain a long-standing challenge in turbomachinery, with the roles of core-flow dynamics and boundary layers still debated. Using a hierarchy of linear stability analysis and two- and three-dimensional URANS simulations, we identify two distinct instability mechanisms and trace them back to their physical origins. The low-flow-rate instability is shown to arise from a two-dimensional inviscid core-flow mechanism, while a new instability, associated with inlet modulation and three-dimensional flow features, is reported at high flow rates.

[Phys. Rev. Fluids 11, 083902] Published Mon Aug 10, 2026

Author(s): Gourab Saha and Kajal Kumar Mondal

Reactive solute transport in open-channel flows is central to understanding contaminant migration in rivers, wetlands, and engineered waterways, but the combined influence of wind-induced shear, porous-bed resistance, and wall absorption has remained unresolved. This study introduces a generalized dispersion model that captures the coupled transient effects of those three influences through analytical transport coefficients and concentration distributions, validated by Brownian dynamics simulations. The findings reveal how wind direction governs pollutant dispersion, retention, and removal, and provides a predictive framework for layered environmental flows.

[Phys. Rev. Fluids 11, 084501] Published Mon Aug 10, 2026

Author(s): Francesco Carbone and Sergio Servidio

In this work, we analyze two-dimensional turbulence in a Galerkin-truncated system with pseudo-logarithmic and random mode selection in Fourier space. The results confirm the presence of the double energy cascade (k−5/3 and k−3) and show how anisotropy influences the organization of vorticity without altering universal scaling laws. Finally, particle pair dispersion follows Richardson superdiffusion (ℓ2(t)∼t3), demonstrating that preserved spectral interactions sustain turbulent transport.

[Phys. Rev. Fluids 11, 084603] Published Mon Aug 10, 2026

Author(s): Conan M. Liptrott, Sandra C. Chapman, Bogdan Hnat, and Nicholas W. Watkins

A scale-by-scale analysis of energy flux in the turbulent cascade can be performed using the spatially filtered magnetohydrodynamic (MHD) equations, while the gradient tensor invariants are widely used to characterize the structure of velocity and magnetic fields. Physical mechanisms responsible for…

[Phys. Rev. E 114, 025102] Published Mon Aug 10, 2026