New Papers in Fluid Mechanics

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

Author(s): Zhaofan Zhu, Haiou Wang, Kun Luo, Jianren Fan, and Evatt R. Hawkes

This study investigates turbulence/flame/wall interaction in turbulent boundary layer combustion with varying wall surface reactivity using direct numerical simulation (DNS). The effects of combustion on the turbulent boundary layer were investigated, revealing that the hairpin vortices of the boundary layer turbulence are lifted upward, upstream of the flame, due to the combustion-induced adverse pressure gradient. The effects of wall surface reactivity on flame/wall interaction were revealed in terms of near-wall heat release rate, wall heat flux and flame quenching behavior.

[Phys. Rev. Fluids 11, 013201] Published Thu Jan 08, 2026

Author(s): B. Davy, C. J. Davies, J. E. Mound, and S. M. Tobias

Rotating Rayleigh–Bénard convection is a key model for rapidly rotating planetary interiors, but direct numerical simulations are restricted by the fine spatial resolution required at small scales. We systematically assess a scale-dependent horizontal hyperdiffusion scheme as a computationally cheaper alternative, comparing 107 simulations against DNS across a wide parameter range. We show that hyperdiffusion can either weaken rotational constraints at low supercriticality or suppress small-scale energy at high supercriticality, and identify parameter choices that preserve large-scale dynamics.

[Phys. Rev. Fluids 11, 013502] Published Thu Jan 08, 2026

Author(s): Thijs Varkevisser and Daniel Bonn

Understanding droplet retraction on hydrophobic surfaces is crucial for applications ranging from self-cleaning coatings to inkjet printing. While previous models relied on static wetting properties, we demonstrate that the retraction of viscous droplets is governed effectively by the dynamic receding contact angle. By incorporating this nonequilibrium parameter, we establish a unified scaling law that accurately predicts retraction rates across diverse substrates.

[Phys. Rev. Fluids 11, 013601] Published Thu Jan 08, 2026

Author(s): Taosif Ahsan, Rodolfo Brandão, Benny Davidovitch, and Howard A. Stone

Upon rupture, a planar liquid sheet retracts under capillary forces at its free edge. We develop an asymptotic model for slender and highly viscous sheets, showing that the dynamics are governed by a remote region where viscous and inertial effects balance. There, a conserved quantity reduces the problem to a one-dimensional diffusion equation for the thickness, subject to effective boundary conditions. From this reduced description, we identify and analyze distinct retraction regimes characterized by the time elapsed since rupture and the relative magnitude of the aspect ratio to the Ohnesorge number.

[Phys. Rev. Fluids 11, 014001] Published Thu Jan 08, 2026

Author(s): Xincheng Wang, Huaiyu Cheng, and Bin Ji

Bursting of tip vortex cavities is commonly observed behind marine propellers and is accompanied by a sharp rise in broadband noise, yet its underlying mechanisms remain poorly understood. This work introduces an Euler-Lagrange hybrid simulation to capture the dynamics of tip vortex cavity bursting. The results reveal that bubble-type vortex bursting is the dominant instability mode and that its intensity is strongly correlated with blade-load variations induced by the hull wake.

[Phys. Rev. Fluids 11, 014301] Published Thu Jan 08, 2026

Author(s): Tianyi Bai and Lin Fu

This work introduces an extra input, the near-wall wall-normal velocity fluctuation, to the spectral linear stochastic estimation between inner and outer signals to compensate for the impact of near-wall universal signals while extracting the attached-eddy contribution. Subsequently, the logarithmic decay rate of the streamwise turbulence intensity is revisited. It becomes, overall, much larger after the compensation, which reduces its dependence on the Reynolds number. These results cannot exclude the likelihood of a constant decay rate by a qualitative analysis of linear coherence functions among near-wall streamwise, near-wall wall-normal, and outer streamwise velocity fluctuations.

[Phys. Rev. Fluids 11, 014601] Published Thu Jan 08, 2026

Author(s): Johannes N. Hillestad, Srikar Yadala, Leon Li, R. Jason Hearst, and Nicholas A. Worth

In this paper, the volumetric velocimetry measurement technique Shake-the-Box is applied to the near wake of a model wind turbine to investigate the vortex dynamics present in the wake. The interaction and breakdown of the tip vortices is visualized using three-dimensional iso-surfaces of Lamb vector magnitude, a technique and physical quantity only accessible using volumetric techniques. The paper describes the influence of the tip vortex interaction process on properties of the tip vortex, such as circulation and the circularity and inclination of the tip vortex contour itself.

[Phys. Rev. Fluids 11, 014701] Published Thu Jan 08, 2026