Resolvent analysis is a cornerstone tool for predicting how flows respond to external forcing, but for unsteady flows the choice of linear operator is not obvious. The common mean-flow resolvent, linearized about the time-averaged flow, can misidentify the dominant receptivity mechanisms, whereas the statistically optimal mean resolvent correctly captures physically relevant phenomena such as the vortex pairing in jets presented here. This work introduces a projection method that enables mean resolvent analysis at low computational cost without resorting to adjoint equations about the unsteady attractor, thereby opening a path toward more complex flows.

[Phys. Rev. Fluids 11, 083903] Published Mon Aug 17, 2026

Reactive fronts in porous media are often destabilized by concentration dependent viscosity of the constituent fluids, leading to viscous fingering. These processes are known to be strongly influenced by hydrodynamic dispersion, originating from incomplete mixing at the pore scale. Yet, their impact and the resulting instabilities remain poorly understood. This study combines transient and quasi-steady-state linear stability analysis to reveal how hydrodynamic dispersion and diffusivity contrasts govern the growth and onset of instabilities, providing new physical insights, with potential applications in contaminant remediation, enhanced oil recovery, and carbon sequestration.

[Phys. Rev. Fluids 11, 083904] Published Mon Aug 17, 2026

Classical similarity theory describes the far field of a laminar jet, but not how a finite Poiseuille inlet loses its memory and reaches that state. We develop a self-consistent two-mode analytical model that predicts this pre-asymptotic evolution without empirical fitting. The theory uncovers a universal Reynolds-scaled centerline decay and shows that the transition length grows linearly with Reynolds number, while reproducing full velocity profiles for both round and slot jets in close agreement with Navier–Stokes simulations.

[Phys. Rev. Fluids 11, 084101] Published Mon Aug 17, 2026

Air curtains restrict buoyancy-driven exchange through building doorways, but sealing effectiveness saturates near about 80 to 85% and the transport pathways fluid takes to leak through have remained unclear. We combine large-eddy simulation with Lagrangian particle tracking to follow individual fluid parcels, classifying their trajectories into three pathways: a gravity current active only before the curtain establishes, and two turbulent-entrainment routes that dominate afterward. Once the curtain is established, the residual leakage is shown to be governed by entrainment at the jet interface rather than by buoyancy.

[Phys. Rev. Fluids 11, 084504] Published Mon Aug 17, 2026

The velocity law of the wall is a well-known law for wall turbulence. In compressible turbulence, the temperature law of the wall is also of interest, but its overall accuracy is inferior to its velocity counterpart. We propose to construct the compressible law of the wall for heat energy using total enthalpy. A semilocal total enthalpy transformation of no fitted parameters is constructed for channel flows, which is structurally analogous and comparable in accuracy to the Trettel–Larsson velocity transformation. This new transformation can potentially serve as a wall model for energy equations to accurately predict the enthalpy or temperature in compressible turbulence.

[Phys. Rev. Fluids 11, 084608] Published Mon Aug 17, 2026

The offshore wind industry is expanding in deep, seasonally stratified waters, where infrastructure-induced mixing may alter ocean dynamics and ecosystems. We present the first fully structure-resolved direct numerical simulations of stratified flow past a vertical cylinder as an idealized model for flow interactions with offshore wind foundations. We identify two distinct wake regimes: a weakly stratified regime characterized by a narrow turbulent wake, and a strongly stratified regime characterized by thermocline-spanning recirculation cells and stationary internal waves, providing a new mechanism for far-field energy transport and a possible explanation for wake persistence discrepancies.

[Phys. Rev. Fluids 11, 084802] Published Mon Aug 17, 2026

This study investigates nonaxisymmetric shape oscillations of an inviscid droplet. A highly accurate Galerkin framework is extended to fully three-dimensional droplet oscillations, and modal coupling is examined for different initial configurations, beginning with four nonaxisymmetric initial shapes (see Figure). The results show that the droplet keeps the symmetries of its initial shape and velocity throughout the oscillation. Only those modes that exhibit all symmetries of the initial configuration are excited. Conversely, modes which violate the symmetries are not excited.

[Phys. Rev. Fluids 11, 083602] Published Fri Aug 14, 2026

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 (${\ell }^2(t)\sim t^3$), demonstrating that preserved spectral interactions sustain turbulent transport.

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

Capillary attachment is a fundamental phenomenon in microengineering, yet the lack of comprehensive theories makes it difficult to predict a pendant drop’s particle-lifting capability. We investigate the critical roles of stability in this process, specifically addressing how to maximize lifting capacity. Our work establishes the theoretical framework required to successfully lift particles in practical applications.

[Phys. Rev. Fluids 11, 084001] Published Fri Aug 07, 2026

Direct numerical simulations reveal the orientation and transport of spherical, spheroidal, and rod-like gyrotactic microswimmers in three-dimensional turbulence. Strongly gyrotactic swimmers preferentially align with the vertical, while weakly gyrotactic swimmers are nearly isotropic. Rod-like swimmers are more strongly affected by fluid shear and align with the principal strain direction. Orientation correlations depend on the gyrotactic response time, and all shapes transition from ballistic to diffusive transport. A reduced two-dimensional model for spherical swimmers reproduces the key statistics.

[Phys. Rev. Fluids 11, 084602] Published Tue Aug 04, 2026

The ability of red blood cells to deform under shear flow is critical to cardiovascular function, yet capturing their complex fluid-structure interactions remains challenging. We extend a perturbative approach to capture cellular enucleation, and probe the emergence of shape instabilities under shear flow. This method isolates how a cell’s initial orientation, membrane mechanics, and viscosity contrast drive morphological instabilities, such as stomatocytes and trilobes. Ultimately, this framework provides a baseline for understanding how disorders like sickle cell disease and malaria compromise cells dynamics.

[Phys. Rev. Fluids 11, 083601] Published Mon Aug 03, 2026

Rayleigh-Taylor mixing is important in natural phenomena and engineering applications, but limited spatial resolution in practical experiments and simulations constrains studies of this mixing process. Resolution-limited fields preserve only large-scale features such as mean profiles and mixing widths, but fail to resolve small-scale structures, resulting in lower fluctuation variance and higher apparent mixedness. Convolutional neural network (CNN) based superresolution reconstructs multiscale flow fields and recovers mixedness evolution, with robust generalization across unseen phases and flow parameters.

[Phys. Rev. Fluids 11, 083901] Published Mon Aug 03, 2026

The turbulent flow beneath a water surface is difficult to measure directly, yet it governs important processes such as mixing and air–water gas exchange. We show that the SHallow REcurrent Decoder (SHRED), a lightweight recurrent neural network, can reconstruct subsurface turbulent flow fields using only three sparse measurements of the surface height. The method performs well on both numerical simulations and laboratory experiments, highlighting its potential for future remote sensing of rivers and other free-surface flows.

[Phys. Rev. Fluids 11, 084601] Published Mon Aug 03, 2026

We study how viscoplastic filaments retract and break. Unlike Newtonian liquids, viscoplastic fluids can resist motion through a yield stress. We identify two mechanisms that can prevent droplet detachment from its edge depending on the shear-dependence: shear thickening reopens due to generation of vorticity near the neck, whereas strong shear-thinning allows capillary pressure to reopen it due to curvature changes. Remarkably, this latter mechanism also arises in the Newtonian limit as the viscosity approaches zero, demonstrating that an almost inviscid filament need not undergo classical end pinching, contrary to the prevailing picture in the literature.

[Phys. Rev. Fluids 11, 073303] Published Thu Jul 30, 2026

In this work smectic bubbles with millimeter diameters, but only nanometer film thicknesses, are exposed in microgravity experiments to high electric fields to study field effects on film inclusions. The observed motion of islands and droplets in the film plane can be considered as a quasi-two-dimensional analogue of electrospraying. Different mobilities of anions and cations of the ionic dopants make the effect polarity dependent. The image shows the motion of islands (color coded blue to brown) when a high electric field at the anode (brown bar) is switched off at time $t=0$.

[Phys. Rev. Fluids 11, 073606] Published Thu Jul 30, 2026

Water injection is a promising technology for mitigating pollutant emissions from hydrogen combustion. However, the high reactivity and diffusivity of hydrogen flames make droplet–flame interactions particularly intricate. Using two-dimensional detailed-chemistry simulations, we show that a single droplet locally modifies the flame displacement speed and heat release rate, while altering flame stretch through droplet-induced curvature. We also propose a phenomenological model to predict the local flame displacement and velocity during the droplet-flame interaction.

[Phys. Rev. Fluids 11, 073201] Published Wed Jul 29, 2026

Why do clean spherical bubbles spread laterally even after they leave each other’s wakes? Experiments and reduced-order modeling reveal that bubble chains disperse through two successive mechanisms: wake-induced lift initiates lateral dispersion, while a bubble-induced upward flow drives the second stage. The findings reveal how pairwise wake interactions give rise to collective bubble dynamics.

[Phys. Rev. Fluids 11, 073604] Published Wed Jul 29, 2026

The sound produced by a detaching bubble is known to arise from its volumetric oscillations, but the factors driving the oscillation amplitude has remained an open question. We perform experiments using two bubble-generation methods, and observe that both the shape and amplitude of the pressure signal depend strongly on the bubble formation mechanisms. Using a large set of experimental data, we identify that the oscillation amplitude is mainly controlled by the initial growth velocity of the bubble. Furthermore, we propose a simple model that captures the onset of the acoustic signal as a consequence of the bubble pinch-off dynamics.

[Phys. Rev. Fluids 11, 073605] Published Wed Jul 29, 2026

We study collisions of small inertial particles suspended in a background flow. These particles may be inert plankton in the ocean or water droplets in clouds. Previous studies have shown that such collisions or caustics require particles to pass through regions of high strain in the flow. Our work finds that the type of strain is crucial, not just its magnitude. Regions of large compressive strain trigger caustics, whereas particles survive caustics despite encountering large strain if they come from extensional strain. Extending the study of caustics to finitely dense particles, we show that the level of strain required for caustics increases with decreasing particle density.

[Phys. Rev. Fluids 11, 074304] Published Wed Jul 29, 2026

We introduce a sequential approach to augment the shear stress transport-conditioned (SST-CND) model, which was originally trained on 2D flows, in 3D scenarios. 3D field inversion is first performed to obtain the distribution of the augmentation term. Then, features that are nonzero only in 3D scenarios are selected to build the expression using symbolic regression. The resultant SST-CND3D model preserves the original model’s capabilities in 2D flows, while showing significant improvement in 3D complex cases, including a real-world high-lift device.

[Phys. Rev. Fluids 11, 074607] Published Wed Jul 29, 2026

Acoustic liners are widely used for noise reduction in aero-engines, but the physical mechanisms governing their aerodynamic drag remain insufficiently documented. Based on pressure-drop measurements in a turbulent channel over a wide range of Reynolds numbers, this study identifies distinct drag regimes and reveals two markedly different behaviors within the transitional regime. In particular, large drag increases are shown to be associated with the onset of aeroacoustic resonance at the liner resonance frequency, while the relative importance of liner geometry is captured through a frontal-solidity-based parameter.

[Phys. Rev. Fluids 11, 074608] Published Wed Jul 29, 2026

[Phys. Rev. Fluids 11, 079901] Published Wed Jul 29, 2026

We embark on a 30-day journey following the flow of a high-viscosity liquid through a capillary tube to assess how existing theoretical models, which also account for the dynamic nature of the contact angle, perform in long-term imbibition processes. The journey reveals the persistent and diffusive nature of imbibition processes for liquids with extreme values of viscosity.

[Phys. Rev. Fluids 11, L072001] Published Wed Jul 29, 2026

A wind-turbine wake in a pressurized-air wind tunnel was forced via slow periodic oscillations in the turbine rotation rate. Flow measurements identified traveling waves in the wake, which could be controlled by independently varying the turbine thrust and tip-speed ratio. The results demonstrate the importance of advection for the modeling and control of wind-turbine wakes, even at nominally quasi-steady time scales.

[Phys. Rev. Fluids 11, 070501] Published Tue Jul 28, 2026

Shear-thinning is ubiquitous in biological and industrial fluids, yet its influence on the instability of time-periodic shear flows remains poorly understood. Using Floquet stability analysis of the Stokes layer in Carreau fluids, we show that shear-thinning can either suppress or promote instability depending on the characteristic fluid response time. The study further identifies a phase-dependent energy-transfer mechanism governing instability in a time-periodic shear flow, which has not been revealed in the literature, providing a dynamic counterpart to the classical energy-production mechanism in steady shear flows.

[Phys. Rev. Fluids 11, 073902] Published Tue Jul 28, 2026

Oscillatory flows in compliant channels are common to a number of soft-hydraulic problems, from physiological transport to microfluidics. Recently, elastoinertial rectification was shown to lead to streaming in these systems. We develop this theory for a two-dimensional (2D) channel with a confined, nearly incompressible elastic layer as its wall and validate the predictions against detailed Lagrangian–Eulerian fluid–structure interaction simulations. Surprisingly, the nearly incompressible 2D layer introduces new physics: resonance-like amplification of streaming at specific Womersley numbers. Our results offer design principles for optimizing flow rectification in soft microsystems.

[Phys. Rev. Fluids 11, 074102] Published Tue Jul 28, 2026

A previously undocumented Reynolds-number-dependent transition is identified in the wake of a rounded-edge slanted afterbody, from a centerline-separated to a novel centerline-attached vortex state. The transition produces a pronounced drag reduction through the collapse of the centerline recirculation region as the upstream boundary layer becomes turbulent. These findings explore experimental evidence linking laminar separation bubble dynamics, shear-layer instability, and wake-state transitions in this canonical bluff-body geometry.

[Phys. Rev. Fluids 11, 074702] Published Tue Jul 28, 2026

The comprehensive statistics of a turbulent flow field can in principle be captured by Hopf’s functional approach; however, the resulting functional equations have remained largely intractable. We here study a simplified passive vector model, whose Hopf equation is solved exactly by an ensemble of Gaussian fields. Based on both theory and simulations, we find that the model displays a fluctuating energy flux from large to small scales. The resulting intermittency at the small scales can be understood as arising from a probabilistic mixture of Gaussian sub-ensembles.

[Phys. Rev. Fluids 11, 074606] Published Thu Jul 23, 2026

Put a soap bubble in an electric field and it stretches into a taller, smooth dome. Turn the field up and, past a critical point, the top sharpens into a pointed cone that fires off a thin jet. Imaging the bubble from the side, we follow this whole sequence in one experiment and find two things. Bubbles of different sizes deform along the same curve once the field is rescaled by bubble size and surface tension, so one balance between electric and capillary forces sets the shape. And the cone is far sharper than Taylor’s classic value, because it is selected while the film is still rushing toward the jet rather than resting in equilibrium.

[Phys. Rev. Fluids 11, 074003] Published Wed Jul 22, 2026

Droplet mixing is vital in many practical applications, yet the underlying physical mechanisms remain poorly understood. This work uses carefully validated numerical simulations to investigate the mixing dynamics of inkjet printed droplets. Our results show that impact-driven flows contribute only weakly to mixing, while molecular diffusion governs homogenization over a timescale of seconds. We perform studies to understand how droplet size, spacing, volume ratio, and substrate wettability influence mixing, producing methods to estimate mixing times for droplet-based manufacturing processes.

[Phys. Rev. Fluids 11, 073603] Published Tue Jul 21, 2026

Rotating bluff bodies are widely used to control wake instabilities and fluid forces, but the role of wake–body interactions in multi-body configurations remains less understood. Direct simulations of isolated and tandem transversely rotating spheres show that rotation can suppress classical shedding and reorganize the wake into double-threaded vortical structures. However, tandem interactions can overturn this stabilizing effect, sustaining unsteady wakes and strongly modulating drag and lift.

[Phys. Rev. Fluids 11, 074101] Published Tue Jul 21, 2026

High-fidelity simulations have become indispensable for uncovering the physics of turbulent two-phase flows, yet quantitative guidelines for the grid and time-step requirements needed to accurately resolve interface dynamics have been lacking. We derive scaling laws that predict these computational requirements as functions of Reynolds, Weber, and Capillary numbers; identify distinct inertia- and viscous-dominated regimes; and introduce a new dimensionless parameter that unifies their classification. The resulting framework provides practical $a$ $priori$ resolution criteria and computational cost estimates for predictive interface-resolved simulations.

[Phys. Rev. Fluids 11, 074303] Published Mon Jul 20, 2026

Invariants, such as energy or enstrophy, are central to turbulence theory. Some systems behave in a sub-space between two well-known limits where invariants are known. Here, we demonstrate that invariants can also be defined for these intermediate cases. Knowledge of the invariants enables the development of simple models for the multiscale dynamics of such systems.

[Phys. Rev. Fluids 11, 074605] Published Fri Jul 17, 2026

Using direct numerical simulations of incompressible turbulence at Taylor-scale Reynolds numbers $R_{\lambda }$ up to about 1740, we examine spectra, two-point correlations, and second-order local-average moments of the energy dissipation rate ϵ and enstrophy Ω. Correlations and local-average moments exhibit larger scaling exponents for fluctuating fields than for total fields over nearby but distinct ranges. In both statistics, squared-mean contributions are nonnegligible relative to fluctuating contributions. Thus, total- and fluctuation-field exponents need not coincide over these ranges. Results suggest $R_{\lambda }$ ≈ 1740 remains insufficient to reach the asymptotic regime assumed in intermittency theories.

[Phys. Rev. Fluids 11, 074603] Published Thu Jul 16, 2026

Data assimilation and symbolic regression are used to formulate an analytical correction to the Spalart-Allmaras model, addressing local deficiencies in its production term. The correction improves separated-flow predictions while preserving the performance of the baseline model for wall-attached flows. Tests on multiple two-dimensional flow cases confirm the applicability of the correction across diverse configurations.

[Phys. Rev. Fluids 11, 074604] Published Thu Jul 16, 2026

Dense non-Brownian suspensions undergo a rheological transition with increasing shear rate, from a Newtonian scaling where stress grows linearly, to a Bagnoldian scaling where it grows quadratically. For suspensions devoid of frictional contacts due to electrostatic repulsive forces keeping the particles apart, our discrete element simulations reveal the shear rate marking the onset of the inertial regime to exhibit a critical behavior as the suspension approaches jamming. Our results show this criticality to be tied to a diverging microstructural length scale, larger than any individual particle, that governs the emergence of inertial effects within the suspension.

[Phys. Rev. Fluids 11, 074302] Published Wed Jul 15, 2026

Using qualitative flow diagnostics and quantitative pressure measurements, this study investigates hypersonic flow over a cone-mounted axisymmetric cavity to assess the influence of Reynolds number, aspect ratio, and excess rear-face height. A distinct mode-shifting behavior from flapping-dominated to Kelvin-Helmholtz-dominated oscillations is identified at the highest aspect ratio, owing to a possible turbulent transition of the shear layer with a change in Reynolds number, which is found to be absent in the two-dimensional cavity configuration. The excess rear-face-height cases also demonstrate the ability to alter the dominant instability mechanism and resonance characteristics.

[Phys. Rev. Fluids 11, 073401] Published Tue Jul 14, 2026

Electrophoresis is often used in combination with external flows for enhanced particle separation. However, the resulting motion when particles have nonuniform surface charge remains poorly understood. This dynamic problem is solved here using an efficient and exact reduced order model. It reveals the diverse set of trajectories emerging from the coupling between the particle’s rotation and its uneven surface charge with potential applications in medical diagnosis and analytical chemistry.

[Phys. Rev. Fluids 11, 073702] Published Tue Jul 14, 2026

Low Reynolds number airfoils may stall abruptly due to laminar separation bubble bursting. Periodic boundary layer forcing can promote transition through the excitation of natural instabilities, and thereby delay or prevent stall. In this study, forcing is provided by a plasma actuator and the influence of varying forcing amplitude on the bursting transient is examined using particle-image velocimetry and surface pressure measurements. Increasing the forcing amplitude delays and increases the variance in the bursting start time. However, the dynamics of the bursting process are largely insensitive to forcing amplitude. For higher forcing amplitudes, bursting is entirely prevented.

[Phys. Rev. Fluids 11, 073901] Published Tue Jul 14, 2026

In multiphase turbulent flows, kinetic and interfacial energies usually coexist in a subtle balance, but their mutual conversion often goes unnoticed in statistically steady regimes. Our work introduces a controlled, time-periodic forcing to break this steadiness, thereby revealing the dynamic cycle of energy injection, conversion, and dissipation. By extending the $k-ϵ$ model to include surface energy and nonequilibrium effects, and by linearizing the system, we uncover the intricate time scales that govern the coupling between these processes.

[Phys. Rev. Fluids 11, 074002] Published Tue Jul 14, 2026

The pinch-off of drops and bubbles from a needle are classic examples of hydrodynamic singularities, in which a fluid body splits into two. While even small amounts of polymers strongly delay drop breakup by forming long liquid threads, recent experiments show that bubble pinch-off remains largely unaffected. In this article we demonstrate that polymer stretching cannot compete with the violent inertial collapse governing bubble pinch-off. Only for sufficiently high polymer concentrations and small needle sizes can viscoelastic effects delay breakup, resulting in the formation of air cavities.

[Phys. Rev. Fluids 11, 073302] Published Mon Jul 13, 2026

We experimentally and numerically investigate nanosecond laser-induced jetting dynamics of a free-falling micro-sized liquid tin droplet. Following laser impact, the droplet rapidly expands and retracts, leading to the formation of a high-speed axial jet. A specific combination of laser-induced pressure and its angular distribution on the droplet surface drives cavity formation, ultimately giving rise to a singular jet. We reveal the underlying mechanism and construct a phase diagram explaining jet emergence as the result of a subtle interplay between droplet curvature during retraction and radial flow.

[Phys. Rev. Fluids 11, 073602] Published Mon Jul 13, 2026

Charge transfer between particles is believed to strongly influence the mechanical properties of many suspensions, yet it remains difficult to observe directly. We demonstrate that biopolymer microcapsules exhibit a unique bouncing dynamics under an alternating electric field that is consistent with repeated charge transfer during contact. These findings identify Coulombic interactions as the origin of the attractive forces responsible for the fragile gel behavior and yield stress previously observed in suspensions of these microcapsules.

[Phys. Rev. Fluids 11, 073701] Published Mon Jul 13, 2026

Controlling the distribution of colloidal particles during drying of a thin porous medium is of importance for various technological applications. The liquid phase distribution during drying in a thin system is strongly affected by two effects, referred to as the edge and breakthrough effects. The impact on the colloid distribution during drying of both effects is studied. Simulations indicate markedly more uniform colloid spatial distributions as the result of both effects compared to predictions based on the standard model ignoring these effects.

[Phys. Rev. Fluids 11, 074301] Published Mon Jul 13, 2026

Particle-vortex interactions in quantum turbulence are essential for interpreting the results from particle-laden experiments in superfluid He II thermal counterflow. In this experimental investigation, we extracted and analyzed trapping and de-trapping processes of small particles on quantum vortex lines. Our results show an asymmetry between the two processes, indicating that they are governed by distinct physical mechanisms, and suggest that they exhibit self-similar features across small time lags. These results deepen our understanding of trapping and de-trapping processes of particles, and the dynamics of particle motion in turbulent thermal counterflow under two-fluid interactions.

[Phys. Rev. Fluids 11, 074602] Published Mon Jul 13, 2026

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

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

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

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

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

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

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

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

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

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

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

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

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

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

This work develops a linear model under a “total transmission” condition that isolates adjacent and cross-interface couplings in a three-interface system by suppressing reverberating waves. We then demonstrate bidirectional modulation of interface evolution by layer spacing and initial amplitude, showing that coupling can either stabilize or destabilize interfaces. Finally, we analytically derive “freeze-out” criteria for single-interface stagnation via parameter tuning and validate it numerically. These results advance multilayer Richtmyer-Meshkov instability physics, provide control strategies for shock-accelerated mixing in inertial confinement fusion, and impact reflected-wave studies.

[Phys. Rev. Fluids 11, 063902] Published Thu Jun 25, 2026

Resolving the near-wall motion of self-diffusiophoretic Janus particles is numerically challenging because of the steep solute concentration gradients within the narrow gap. We develop an asymptotic theory in the distinguished limit where the inert face is comparable in size to the lubrication region. For axisymmetric and slightly tilted configurations, we obtain explicit particle velocities and gap concentration fields that reveal how cap size influences the particle’s rotational stability near the wall.

[Phys. Rev. Fluids 11, 064103] Published Wed Jun 24, 2026

We show that the spread of infinitesimal perturbations in a turbulent density-stratified fluid becomes slower with increasing degree of stratification. With a higher degree of stratification, the spatial growth of the uncertainty gets more and more compressed along the direction of stratification. Despite this, the temporal growth of perturbations follows the same universal behavior: an initial decay followed by an exponential growth, ultimately leading to saturation. The rate of growth of the perturbation, however, gets affected by stratification through the strain-mediated dynamics of the underlying velocity field, rather than through direct coupling with the density fluctuations.

[Phys. Rev. Fluids 11, 064615] Published Tue Jun 23, 2026

While droplet impact on liquid pools is well studied for Newtonian fluids, particle suspensions introduce complex non-Newtonian dynamics. This work experimentally identifies five distinct impact regimes for cornstarch suspension droplets, revealing unique phenomena like “wrapped bubbles” and impact-induced jamming that are absent in simple fluids. Through an energy balance analysis, the authors demonstrate that these behaviors are dictated by a direct competition between pool cavity dynamics and suspension rheology. The resulting transition boundaries offer practical guidance for engineering applications like 3D printing.

[Phys. Rev. Fluids 11, 060501] Published Mon Jun 22, 2026

We propose a moment gas kinetic flux solver (MGKFS). Like conventional GKFS, the governing equations for mass, momentum, and energy are still solved by the finite volume method (FVM). In addition, a set of evolution equations for stresses and heat fluxes are also solved by FVM, in which numerical fluxes are evaluated by high-order moments of the distribution function at cell interfaces. That is, high-order moment equations are directly computed via moment integration of a reconstructed gas distribution function at cell interfaces. This strategy not only provides a new closure method for the 13-moment system, but also avoids tedious boundary conditions for stress and heat flux equations.

[Phys. Rev. Fluids 11, 063401] Published Mon Jun 22, 2026

Rayleigh–Darcy convection (RDC) in porous media controls mass and heat transfer in many geological systems. We show that permeability heterogeneity fundamentally reshapes RDC. The permeability correlation length interacts with intrinsic flow-structure scales that determine the convection pattern. High-resolution simulations reveal three distinct heterogeneity regimes depending on Rayleigh number (Ra): (i) At low Ra stable convection cells are constrained; (ii) At intermediate Ra microplume-driven transport is enhanced; and (iii) At high Ra heterogeneity becomes negligible or boundary-layer-controlled. This provides theoretical support for predicting convective mixing and scalar transport.

[Phys. Rev. Fluids 11, 063502] Published Mon Jun 22, 2026

We experimentally investigate the detachment of a bubble injected from an orifice on a horizontally moving plate. By performing theoretical analysis based on force balance without empirical constants, we introduce a dimensionless parameter $R_c$ that characterizes a transition between vertical buoyancy-dominated “rise” and horizontal shear-dominated “lift-off” regimes. $R_c$ successfully captures the trends of both the bubble radius and inclination angle at detachment across all experimental conditions, and $R_c$ = 0.8 indicates the transition boundary between the two regimes.

[Phys. Rev. Fluids 11, 063604] Published Mon Jun 22, 2026

Hydrodynamic metamaterials can steer liquids without disturbing surrounding flow, but passive designs have largely been limited to fixed environments and regular geometries. We show that extreme effective viscosity anisotropy, realized through simple microchannel height modulation and solid barriers in Hele-Shaw flows, decouples a metashell’s performance from the background viscosity. The resulting free-form metadevice remains invisible under environmental changes while accelerating flow in its core, as verified by simulations and experiments, opening a route to robust microfluidic control.

[Phys. Rev. Fluids 11, 064101] Published Mon Jun 22, 2026

This study investigates a novel fluid–flexible filament system in which the filament is allowed to move laterally in a uniform flow. Once symmetry breaking occurs, the filament exhibits spontaneous and sustained translation, effectively self-propelling by extracting energy from the flow. The dynamics are governed primarily by the effective Reynolds number and effective bending stiffness. A reduced-order parameterized model is further developed to predict the filament’s equilibrium configuration and curvature.

[Phys. Rev. Fluids 11, 064102] Published Mon Jun 22, 2026

Electric field–driven droplet generation provides an active strategy for overcoming the limited controllability of conventional passive microfluidic methods; however, the mechanisms governing mode transitions under different combinations of electrical properties remain unclear. Here, we develop a coupled lattice Boltzmann–finite difference numerical framework to investigate electrohydrodynamic droplet formation in T-shaped microchannels under varying electric field strengths, permittivity ratios and conductivity ratios. We identify four droplet generation modes and reveal their transition mechanisms by analyzing interfacial charge distributions and electric-field forces.

[Phys. Rev. Fluids 11, 064202] Published Mon Jun 22, 2026

This study investigates the diffusiophoresis of charged rigid colloids in yield-stress viscoplastic fluids using fully coupled electrokinetic simulations supplemented by thin-double-layer analysis, and demonstrates new avenues for manipulating particles in complex viscoplastic media. The results show that shear-thinning rheology enhances particle velocity significantly, whereas yield stress suppresses particle mobility and can even induce stalling. In shear-thinning fluids, a reversal of diffusiophoretic motion is observed at lower values of the flow consistency index, which is suppressed when diffusion-dominated transport is amplified for multivalent electrolytes or at higher yield stresses.

[Phys. Rev. Fluids 11, 064203] Published Mon Jun 22, 2026

Particle-shape symmetry determines the form of inertial hydrodynamic forces and torques acting on particles settling in a quiescent fluid. Exploiting these symmetries provides a systematic way of analyzing how particle shape influences unsteady settling dynamics, by classifying particles according to their shape-symmetry groups. Our results help to understand the connection between particle geometry and the transient dynamics observed in settling experiments with particles of different shapes.

[Phys. Rev. Fluids 11, 064305] Published Mon Jun 22, 2026

We propose a continuum two-dimensional model for cohesive granular flows down inclines. Using the Contact Dynamics method, we explore the parameter space of inclination angle and adhesion strength for which steady uniform flows develop. We then compare free-surface velocity and plug thickness with the model. We find that, at moderate inertial numbers $I$, the flow rheology can be described by a linear $\mu (I)$ friction law supplemented by a macroscopic cohesive stress. The independence of friction and adhesion is confirmed within the investigated parameter range, and the macroscopic cohesive stress is found to scale linearly with local contact adhesion, in agreement with Rumpf’s prediction.

[Phys. Rev. Fluids 11, 064306] Published Mon Jun 22, 2026

We outline a workflow for examining statistically transient fluid flows, which eludes most standard modal analysis techniques. As a challenging example, we investigate the transient dynamics of a turbulent supersonic twin-rectangular jet flow. Forcing-induced perturbations are extracted using synchronized large-eddy simulations (LES) of the natural and forced jets, and a database is collected that captures an ensemble of realizations of these perturbations. From this ensemble, we study the time-varying mean flow deformation and perform space–time proper orthogonal decompositions.

[Phys. Rev. Fluids 11, 064614] Published Mon Jun 22, 2026

[Phys. Rev. Fluids 11, 069902] Published Mon Jun 22, 2026

Choanoflagellates, key marine microscopic filter feeders, display large diversity in their filter geometry. Comparing a simplified infinite cylindrical model for the filter with biological, we find that many choanoflagellate species exist near a ridge in the effective flux into the filter but away from a similar ridge in the power. This contrasts with the existing hypothesis that the pressure drop is roughly constant over different species.

[Phys. Rev. Fluids 11, 063102] Published Thu Jun 18, 2026

Collective locomotion of swimming and flying animals is fascinating in terms of individual-level fluid mechanics and group-level structure and dynamics. Here we bridge and relate these scales through a formation-flight model that views the collective as a material whose properties arise from flow-mediated interactions among its members. Our model shows that the group behaves as a soft “crystal” with regularly spaced member “atoms” whose positioning is susceptible to deformations and dynamical instabilities. Other emergent properties relevant to biological collectives include group cohesion, sensitive detection of and response to perturbations, and information transfer through traveling waves.

[Phys. Rev. Fluids 11, 063103] Published Thu Jun 18, 2026

Electrokinetic transport at liquid-liquid interfaces offers new routes for active microfluidic control, but practical use on slippery liquid-infused surfaces (SLIS) remains limited. Using direct numerical simulations, this work reveals two key regulation mechanisms, includign electroosmotic velocity reversal driven by groove oil depletion and a two-sided streaming potential effect from ion partition. These findings provide design principles for enhancing liquid pumping, energy conversion, and lab-on-a-chip devices in real-world multiphase systems.

[Phys. Rev. Fluids 11, 063702] Published Thu Jun 18, 2026

The von Kármán sodium experiment provided the first laboratory observation of magnetic field reversals reminiscent of those occurring in planetary dynamos. Using realistic numerical simulations robust across two independent solvers, we identify the mechanism underlying these reversals. The dynamics result from the coupling of dipolar and quadrupolar magnetic modes through two large-scale velocity modes, one of which breaks the flow symmetry. During a reversal, the magnetic field first localizes near one impeller, then evolves through a transient quadrupolar state before localizing near the opposite impeller and ultimately recovering as a dipole of reversed polarity.

[Phys. Rev. Fluids 11, 063703] Published Thu Jun 18, 2026

We study a fluid close to its critical point where the liquid-vapor phase boundary ends and the distinction between gas and liquid disappears. The compressible Navier-Stokes-Korteweg equations are solved with a van der Waals equation of state. Density-stratified basic states due to gravity are computed numerically. Numerical simulations confirm the propagation of acoustic waves in the supercritical case above the critical point. For the subcritical case we find spinodal decomposition for a randomly distributed initial density. Additionally, we consider the Rayleigh-Taylor instability in detail, both by a linear stability analysis and by direct numerical simulations.

[Phys. Rev. Fluids 11, 064004] Published Thu Jun 18, 2026

This study follows the interplay between velocity structures and concentration structures to explain the pattern of pollution behind a vehicle. Measurements of concentration, along with PIV measurements, show the effects of vehicle and wake topologies on pollutant dispersion.

[Phys. Rev. Fluids 11, 064503] Published Thu Jun 18, 2026

The space-time variations of wall-pressure fluctuations (p_w) provide key insights into the dynamics of turbulent boundary layers, yet accurate measurements of their large-scale frequency-wavenumber spectrum remain challenging at high friction Reynolds numbers (Re). Using a bespoke 63-microphone array designed to resolve the large-scale p_w field with minimal aliasing errors, we report novel measurements spanning across 1400 < Re < 5200. The results reveal that p_w scaled on the boundary-layer thickness is most strongly correlated with turbulence in the logarithmic region, identifying it as the dominant source of large-scale scale p_w relevant to turbulence sensing, modeling, and control.

[Phys. Rev. Fluids 11, 064612] Published Thu Jun 18, 2026

Cloud supersaturation is modeled as a passive scalar with a phase-relaxation time under a uniform vertical gradient. Large eddy simulations with grid points of ${1024}^3$ confirm the theoretical prediction that one $-5/3$ spectrum by the phase relaxation and another by the turbulence cascade coexist at low and high wavenumbers in the inertial range, respectively. As the phase relaxation time becomes shorter the transition wavenumber between the two ranges shifts to higher wavenumbers, consistent with theory. Probability density function tails of the supersaturation at small-scales become longer than that of the velocity, stronger intermittency, as the phase relaxation time becomes longer.

[Phys. Rev. Fluids 11, 064613] Published Thu Jun 18, 2026

We characterize the three-dimensional shape of an elastic, transparent sheet as it translates, rotates, and deforms - a key experimental challenge in the study of particle-laden flows – with a high-resolution, single-camera method. We scan the object nonintrusively to capture its illuminated surface and couple the space-time representation of its surface with a neural autoencoder to reconstruct the 3D shape of the object. This method enables the study of motion and deformation of objects with a wide range of surface geometries.

[Phys. Rev. Fluids 11, 064901] Published Thu Jun 18, 2026