Latest papers in fluid mechanics

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

Author(s): Hugo Felippe da Silva Lui and William Roberto Wolf

Shock–boundary layer interactions over the convex wall of a supersonic turbine vane are explored through a detailed analysis of extreme separation bubble events. By conditionally sampling expanding and contracting bubble states and using finite-time Lyapunov exponents together with a deforming control-volume framework, this study reveals how near-wall streaks and streamwise vortices influence the separation bubble unsteadiness and the mass flux along its surface.

[Phys. Rev. Fluids 11, 013401] Published Tue Jan 13, 2026

Author(s): Rishish Mishra, Harish Pothukuchi, Harinadha Gidituri, and Juho Lintuvuori

The interface crossing behavior of a microswimmer is strongly dependent upon the capillary number (Ca), which is defined as the ratio of swimming to interfacial forces. When the interfacial forces dominate, the swimmer gets trapped. We propose a model, where the swimmers are trapped due to a wetting-induced thermodynamic potential. The translational motion of a prolate swimmer is accompanied by reorientation driven by the combined action of hydrodynamic and thermodynamic torques.

[Phys. Rev. Fluids 11, 014002] Published Tue Jan 13, 2026

Author(s): T. Preskett, M. Virgilio, P. Jaiswal, and B. Ganapathisubramani

Smooth and rough wall turbulent boundary layers often occur with external pressure gradients, which affect their development. This work presents an experimental investigation of high Reynolds number boundary layers, focusing on the effect of pressure gradient history on turbulence characteristics. Taking the turbulent spectra, we isolate both the effect of pressure gradient history and how the surface affects the response to a given pressure gradient history. The final part of this work looks at whether it’s possible to capture some of the effects on the turbulence spectra, particularly the peaks present within the spectra.

[Phys. Rev. Fluids 11, 014603] Published Tue Jan 13, 2026

Author(s): Pranav Nath and Jean-Pierre Hickey

The complexity of wall-bounded turbulent flows has given rise to a variety of models that capture the essence of this physical problem. Townsend’s Attached Eddy Model (AEM) utilizes eddies that exhibit geometric scaling with their distance from the wall. In contrast, the One-Dimensional Turbulence (ODT) model is built on a completely different set of modeling assumptions. We re-write the ODT formulation as a Markov process and simplify some modeling assumptions, which allows us to recast the equations into a form analogous to AEM. By distilling and simplifying ODT, we highlight the implicit similarities with the modeling assumptions found in AEM.

[Phys. Rev. Fluids 11, 014604] Published Tue Jan 13, 2026

Author(s): Kai Liu, Wang Xiao, John Lowengrub, Shuwang Li, and Meng Zhao

We investigate the wrinkling dynamics of a long, flat filament immersed in a viscous fluid subjected to compression at a constant rate. Typical wrinkling dynamics proceed through three stages: initiation, development, and relaxation. The first stage, during which high mode perturbations increase exp…

[Phys. Rev. E 113, 015102] Published Tue Jan 13, 2026

Author(s): Yinghui Li, Filippo Coletti, Monika Colombo, Yingchao Meng, and Andrew deMello

In dense suspensions, both rigid particles and deformable red blood cells (RBCs) exhibit a tendency to migrate away from the walls and towards the center of the vessel in which they flow. Here we experimentally investigate the transport of microparticles along with RBCs in bifurcating vessels, which is particularly relevant for targeted drug delivery. Via high-speed imaging and Lagrangian tracking, we observe that particles marginate and form layers adjacent to the sidewalls of bifurcation, while the deformable RBCs populate the center of the vessel. Our results show that the margination behavior of spherical particles is quantitatively controlled by the RBC-to-particle volume ratio.

[Phys. Rev. Fluids 11, 013101] Published Mon Jan 12, 2026

Author(s): Mykola Stretovych, Eddy Timmermans, and Dmitry Mozyrsky

Understanding the dynamics of gas discharges is critical for numerous technological applications. While the physics of electric breakdown in gas, such as air, has been studied for many decades, the early stages of the discharge dynamics remain to be an active subject of research. In this paper we provide a simple approach that helps us understand such early stages of dynamics and explains the structure of the discharge channel at the qualitative level. Comparison with experimental data shows a good agreement of the approach with the measured characteristics, such as discharge current, at small times after the discharge initiation.

[Phys. Rev. Fluids 11, 013202] Published Mon Jan 12, 2026

Author(s): J. O. Oyero and A. De Wit

If a denser solution of a solute A lies above a less dense solution of a solute B in the gravity field, a Rayleigh-Taylor instability can trigger convective motions which favor mixing of the two fluids. We show by numerical simulations that double-diffusive effects occuring when A and B diffuse at different rates can modify the scalings of the onset time and acceleration of the instability. Moreover, the difference in diffusion of the solutes can be used to optimize mixing between the two solutions.

[Phys. Rev. Fluids 11, 013503] Published Mon Jan 12, 2026

Author(s): Zeyang Mou, Zheng Zheng, Zhen Jian, Carlo Antonini, Christophe Josserand, and Marie-Jean Thoraval

The singular collapse of a cavity can produce extremely fast and fine jets from the dynamics of larger systems. These jets have a wide range of applications, from printing technologies to cavitation bubbles or the formation of aerosols. We investigate the formation of extremely fast singular jets generated when a coaxial water‑in‑oil compound drop impacts a solid surface. Experiments and simulations reveal how cavity collapse, controlled by impact velocity and volumetric ratio, produces high‑speed jets and microdroplets. Two distinct collapse regimes emerge, governed by 1/2 and 2/3 self‑similar power laws.

[Phys. Rev. Fluids 11, 013602] Published Mon Jan 12, 2026

Author(s): Haotian Chen, Hanbing Zou, Sheng Xu, and Bing Wang

Using the stiffened-gas equation of state (SG-EOS), we extend the classical shock dynamics theory to underwater scenarios. The Chester-Chisnell-Whitham (CCW) relation and its two-dimensional characteristic relations are systematically modified. We further propose a method of designing a shock tube that transforms planar underwater shock waves into cylindrical ones with pre-set intensity and curvature. Numerical tests demonstrate that the shock intensity and curvature can be accurately controlled to match predicted values. This work provides a theoretical framework for geometric control of shock waves in compressible liquids.

[Phys. Rev. Fluids 11, 014302] Published Mon Jan 12, 2026

Author(s): Xinyi Huang, Sze Chai Leung, and H. Jane Bae

Data-driven subgrid-scale modeling in the large-eddy simulations (LES) suffers from the inconsistency between the a priori tests and the a posteriori tests. We study the difference in filtered high-fidelity data and LES to identify the numerical deviation between the two cases, which is a combined impact of commutation error, numerical errors, and error coupling. By incorporating numerical deviations into model training, we enhance consistency, stabilize simulations, and improve predictions of the a posteriori tests. Our findings highlight that data-driven methods introduce significant nonlinearity and equation coupling, exacerbating inconsistencies compared to non-data-driven approaches.

[Phys. Rev. Fluids 11, 014602] Published Mon Jan 12, 2026

Author(s): Haithem Taha and Kshitij Anand

The main challenge behind simulating incompressible flows is projecting the dynamics on the space of divergence-free fields. This projection is typically achieved by solving the Poisson equation in pressure at every time step. Here, we use the Principle of Minimum Pressure Gradient to formulate this projection as a minimization problem. The flow evolves from one instant to another in a way that minimizes the L2 norm of the pressure force required to satisfy the continuity constraint. We showed that the minimization problem is a convex quadratic programming problem and derived its closed-form solution. Hence, we obtained an explicit form for the projected dynamics of Navier-Stokes.

[Phys. Rev. Fluids 11, 014901] Published Mon Jan 12, 2026

Author(s): L. Manfredini and Ö. D. Gürcan

A shell model can be considered as a self-similar chain of interacting triads, where each triad can be interpreted as a nonlinear oscillator that can be mapped to a spinning top. Investigating the relation between phase dynamics and intermittency in such a chain of nonlinear oscillators, it is found…

[Phys. Rev. E 113, 015101] Published Fri Jan 09, 2026