New Papers in Fluid Mechanics

Author(s): Dongjie Jia, Mohammad Majidi, Kurt D. Ristroph, and Arezoo Ardekani

We used a high-fidelity simulation framework to study the fluid and mixing dynamics inside two turbulent mixers: the multi-inlet vortex mixer (MIVM) and the confined impinging jets mixer, operating under various conditions. We identify differences in turbulence onset, total energy, and mixing performance of two MIVM configurations. This study demonstrates the importance of a high-accuracy numerical scheme for simulating turbulent mixers and understanding performance differences among them.

[Phys. Rev. Fluids 11, 014502] Published Mon Jan 26, 2026

Author(s): Ashish Mishra, Paolo Personnettaz, George Mamatsashvili, Vladimir Galindo, and Frank Stefani

Effect of endcaps are of fundamental interest in Taylor-Couette (TC) experiments, including magnetorotational instability (MRI)-experiments. Understanding their influence on the TC flow dynamics is essential for the interpretation of experimental results. In this work, we studied the endcap effects in a Rayleigh-stable TC flow at high, experimentally relevant Reynolds numbers. The main result is that split-endcaps reduce Ekman pumping in the bulk flow and induce turbulence, which however remains localized in their vicinity. Endcaps modify the mean azimuthal velocity profile that in turn results in the lower threshold of the MRI onset, potentially facilitating its experimental detection.

[Phys. Rev. Fluids 11, 014606] Published Mon Jan 26, 2026

Author(s): Uttam Cadambi Padmanaban, Bharathram Ganapathisubramani, and Sean Symon

Assimilating planar experimental data using standard two-dimensional constraints often distorts the momentum balance, as the model artificially compensates for the lack of divergence in the measurements. We demonstrate that enforcing three-dimensional constraints (3DVar) resolves this ambiguity in deep stall flows. By enabling spanwise flow development, 3DVar balances experimental divergence errors with physical gradients rather than artificial forcing. This isolates measurement inconsistencies from turbulence model deficits, yielding physically consistent reconstructions of unmeasured quantities like pressure and eddy viscosity.

[Phys. Rev. Fluids 11, 014904] Published Mon Jan 26, 2026

Author(s): Yangyang Cao, Alexander Kurganov, Masoud Rostami, Chenxi Wang, and Vladimir Zeitlin

We introduce the Magnetohydrodynamic Thermal Rotating Shallow Water (MTRSW) model, a novel framework for studying thin, magnetized, and stratified fluid layers in geophysical and astrophysical contexts, such as the solar tachocline. This model integrates thermal gradients and magnetic fields with rotation, revealing their coupled impact on stability. Furthermore, we incorporate Hall effects, enabling the model to capture essential small-scale physics like fast magnetic reconnection.

[Phys. Rev. Fluids 11, L011701] Published Mon Jan 26, 2026

Author(s): Praphul Kumar and Jason R. Picardo

Phytoplankton, like dinoflagellates, produce mesmerizing displays of light when subjected to the turbulent flow in breaking waves and ship wakes. Here, we ask how bioluminescence is affected by turbulence, given that dinoflagellates flash with an intensity that increases with both the extent and rate of deformation. Introducing a light-emitting dumbbell as a minimal model, we show that intermittent fluctuations of the velocity-gradient subjects dinoflagellates to bursts of extreme straining, which in turn produces bright flashes. Comparisons with steady and Gaussian-fluctuating flows demonstrate that light emission is strongly promoted by the dissipation-scale intermittency of turbulence.

[Phys. Rev. Fluids 11, L012602] Published Mon Jan 26, 2026

Author(s): Alexandre Vierron and Chérifa Abid

This study investigates the effect of the thermal conductivity of titanium dioxide (TiO2) nanoparticles suspended in water on heat transfer dynamics and the formation of convection cells. Experimental observations reveal that colloidal stability and nanoparticle sedimentation strongly influence the evolution of convection patterns and overall heat transfer. Due to the low particle concentration and small size, a thin heat-conducting sediment layer forms within the thermal boundary layer. This locally enhances the conductive heat flux in the lower boundary layer, leading to an asymmetry in the temperature profile between the top and bottom of the cavity.

[Phys. Rev. Fluids 11, 013505] Published Fri Jan 23, 2026

Author(s): Davis J. Evans, Bauyrzhan K. Primkulov, and John W. M. Bush

Droplets walking on a vibrating liquid bath have provided a platform for exploring the boundary between classical and quantum physics. The system is typically considered with monochromatic bath forcing, in a parameter regime in which the droplets bounce either in-phase or out-of-phase with respect to each other. We demonstrate here that the application of an additional subharmonic forcing allows for control of the droplets’ relative phase. The figure shows (a) an irregular array of bouncing drops in which the leftmost drop (blue) is out-of-phase with its neighbours (red) transforming into (b) an array in which all droplets bounce in synchrony in response to the subharmonic forcing.

[Phys. Rev. Fluids 11, 014003] Published Fri Jan 23, 2026

Author(s): Sihang Liu, Ran Gao, Shuai Yin, Zhi Tao, Haiwang Li, and Yi Huang

Droplet impact on liquid pools has long been analyzed using energy-balance models dominated by inertial and gravitational effects. In the low-Froude-number regime relevant to immiscible droplet encapsulation and interfacial processing, however, the partitioning of impact energy remains poorly understood. Here we show experimentally that, alongside gravitational potential energy, surface energy and viscous dissipation make significant contributions to cavity dynamics. By incorporating cavity shape deviations and viscous losses into a revised energy framework, we establish an improved scaling description for cavity penetration in immiscible liquid impacts.

[Phys. Rev. Fluids 11, 014004] Published Fri Jan 23, 2026

Author(s): Julien Sablon, Jérôme Fontane, Gabriele Nastro, and Laurent Joly

This study examines transient energy growth in a high-Reynolds and high-swirl numbers heavy q-vortex. Through nonmodal stability analysis, we identify optimal perturbations that produce energy amplifications far exceeding adjoint mode predictions over finite time horizons. The analysis reveals a robust three-stage transient mechanism combining pressure-induced energy transfers and a self-sustaining Rayleigh-Taylor feedback loop between radial velocity and density perturbations. This core-centered destabilization mechanism, absent in constant-density vortices, provides new physical insights into short-term energy amplification relevant to aircraft wake dispersion, mixing, and flow control.

[Phys. Rev. Fluids 11, 014703] Published Fri Jan 23, 2026

Author(s): Albert Dombret, Adrien Sutter, Baptiste Coquinot, Nikita Kavokine, Benoit Coasne, and Lydéric Bocquet

Building on a fluctuating Darcy framework, this work shows that porosity fluctuations can strongly and nontrivially reshape the hydrodynamic permeability of a porous matrix or membrane. The permeability is expressed in terms of the matrix fluctuation spectrum, revealing a “frequency‑matching” regime where solid and fluid modes resonate. Exploring different excitation scenarios – breathing matrices, phonon‑like modes and active forcing – unveils new strategies to optimize membrane separation processes and potentially bypass the usual permeability–selectivity trade‑off.

[Phys. Rev. Fluids 11, 014201] Published Wed Jan 21, 2026

Author(s): Guang-Yao Xia, Jian-Zhao Wu, Bo-Fu Wang, Kai Leong Chong, and Quan Zhou

The multistability and bifurcation in thermal vibrational convection have been systematically studied via direct numerical simulations. Two distinct states are clarified: a periodic one with single-roll dominance and higher mean heat/momentum transport, and a chaotic one with multimode interplay. Bifurcations occur primarily near St=1, where resonant sensitivity to initial conditions leads to hysteresis across varying vibrational Rayleigh number and aspect ratio. This work elucidates the underlying mechanisms of flow state transitions, providing a framework for understanding multistability and flow control in unsteady regimes.

[Phys. Rev. Fluids 11, 014401] Published Wed Jan 21, 2026

Author(s): Satori Tsuzuki

Knowing when turbulence reaches peak dissipation matters for theory and for adaptive simulation and measurement strategies. Using direct numerical simulations of the Taylor–Green vortex, we introduce a spectral diagnostic based on the curl-of-vorticity spectrum, equivalent to a k^4-weighted energy spectrum. Its peak wavenumber stabilizes before the dissipation maximum across resolutions. The resulting early-warning signal links spectral evolution to the emergence of filamentary vortical structures and can support adaptive meshing and output scheduling.

[Phys. Rev. Fluids 11, L012601] Published Tue Jan 20, 2026

Author(s): Cal J. Rising, Eric J. Ching, and Ryan F. Johnson

Three-dimensional simulations of a reacting hydrogen jet in supersonic crossflow are performed using a discontinuous Galerkin (DG) method, which is appealing for its high-order accuracy and geometric flexibility. Analysis of the coupled chemistry and compressible flow shows a predominantly non-premixed combustion mode with localized premixed regions. A key result is the accurate prediction of this configuration on a fully unstructured tetrahedral mesh, demonstrating the potential of DG methods to capture complex physics in high-speed reacting flows.

[Phys. Rev. Fluids 11, 013203] Published Fri Jan 16, 2026

Author(s): Feng Wang, Yihong Du, Xueyi Xie, Enrico Calzavarini, and Chao Sun

In this work, we experimentally investigate the freezing and ice aging dynamics in saline water under natural convection. We show that the rapid formation of a mushy ice layer is followed by desalination processes that might lead to a slow asymptotic decrease of the ice thickness. Desalination of mushy ice reduces its porosity, which alters the dynamic thermal equilibrium and ice thickness by weakening buoyancy-driven convection within mushy ice. In turn, changes in brine convection and ice thickness further affect the desalination process. The long-term dynamics can be predicted by a one-dimensional model based on appropriate parameterizations of global heat and mass transfer properties.

[Phys. Rev. Fluids 11, 013504] Published Thu Jan 15, 2026

Author(s): Loïc Rousseau, Laurence Girolami, Mohammed Boussafir, and Frédéric Risso

The dynamics of unconfined, low-inertia, fluidized beds is investigated. The fluidization velocity is well described by a universal function of the volume fraction involving a prefactor that depends on particle inertia, confinement, Reynolds number and inlet flow disturbances. Bed surface oscillations are used to probe concentration fluctuations within the suspension, revealing the role of vertical concentration waves upon the transition toward the heterogeneous regime at low concentrations.

[Phys. Rev. Fluids 11, 014303] Published Thu Jan 15, 2026

Author(s): Prasanna Kumar Billa, Cameron Tropea, and Pallab Sinha Mahapatra

A superhydrophobic sphere entering a quiescent water pool entrains an air cavity whose evolution governs its subsequent dynamics. The cavity remains axisymmetric up to the primary pinch-off, after which multiple pinch-off events occur. For lighter spheres, the entrained air volume can trigger a transition from downward penetration to upward motion due to enhanced buoyancy. Both primary and secondary pinch-offs induce abrupt buoyancy changes and force rebalancing, captured using orthogonal high-speed imaging. The coupling between cavity evolution, pinch-off dynamics, and trajectory reversal depends on impact conditions and sphere density.

[Phys. Rev. Fluids 11, 014304] Published Thu Jan 15, 2026

Author(s): Xiaohua Wu, Carlos A. Gonzalez, and Rahul Agrawal

A comprehensive dataset resulting from DNS of bypass transition in the narrow sense with inlet freestream turbulent intensity (FSTI) levels 0.75%, 1.5%, 2.25%, 3.0%, and 6.0% is reported. It is found that boundary-layer freestream scales evolve similarly to their spatially developing isotropic turbulence flow counterparts. Further, at an intermediate FSTI of 2.25%, two turbulent spot inception mechanisms coexist: the long low-speed streak primary and secondary instabilities (low FSTI) and the self-amplifying process of oblique vortex filaments interacting with a Delta-shaped low-speed patch underneath (high FSTI).

[Phys. Rev. Fluids 11, 014605] Published Thu Jan 15, 2026

Author(s): Kunihiko Taira

Small air vehicles that operate in urban canyons, around mountainous terrains, and in the wakes of marine vessels could encounter highly unsteady atmospheric conditions with relatively strong gusts. The gust ratio can exceed 1 in these extreme flight environments, making stable flight difficult, if not currently impossible. We refer to the study of aerodynamics for gust ratios over 1 as extreme aerodynamics and identify major challenges that require breakthroughs, particularly with data-driven approaches.

[Phys. Rev. Fluids 11, 014702] Published Thu Jan 15, 2026

Author(s): John M. Lawson

The widespread adoption of Lagrangian particle tracking (LPT) and Particle Tracking Velocimetry (PTV) methods motivate the reconstruction of continuous velocity fields from sparse, noisy particle tracking data. This work introduces a physics-informed Gaussian process regression (GPR) framework that incorporates mass conservation, boundary conditions, and statistical symmetries directly into the assimilation process. The method provides optimal interpolation, quantifies prediction uncertainty and estimates two-point velocity covariances. Validated across canonical turbulent flows, GPR significantly outperforms the industry standard, offering improved resolution and predictive accuracy.

[Phys. Rev. Fluids 11, 014902] Published Thu Jan 15, 2026

Author(s): Ludovic Jami, François-Xavier Gauci, Céline Cohen, Xavier Noblin, and Ludovic Keiser

Vascular networks exhibit a remarkable diversity of architectures and transport mechanisms across biological systems. Inspired by embolism propagation in plant xylem, where air invades water-filled conduits under negative pressure, we study air penetration in compliant one-dimensional hydrodynamic n…

[Phys. Rev. E 113, 015103] Published Wed Jan 14, 2026