When determining the authorship list for your next paper, be generous yet disciplined.

On May 29 at noon ET, Michalis Chatzimanolakis (Harvard University) will sit down with the Physical Review Journal Club to discuss their recently published research, “Learning in two dimensions and controlling in three: Generalizable drag reduction strategies for flows past circular cylinders through deep reinforcement learning.” Please register here. Registration is free and a video recording will be provided to all registrants.

We are greatly saddened by the sudden passing on April 14 of Keith Julien, Chair and Professor of Applied Mathematics at the University of Colorado, Boulder, Fellow of the American Physical Society, and a member of the Editorial Board of Physical Review Fluids.

We report a new Mach number invariant function for the mean temperature field in compressible wall turbulence. We demonstrate its validation by comparing it with the invariant functions derived in the previous studies, i.e., the semi-local-type and van-Driest-type scalings, case by case. The newly proposed temperature transformations based on the new scaling show an improvement in channel flows over adiabatic walls and supersonic/hypersonic turbulent boundary layers with cold walls. The effects of the generated high-order terms during derivation are also clarified. These findings may be revealing for the development of the near-wall model in high-speed aerodynamics.

This paper derives the Enskog equation in the context of orthonormal vielbein fields, allowing the use of arbitrary coordinate systems to describe spatial geometry. Additionally, an adapted coordinate system in momentum space is employed, which is connected to physical space via vielbeins. A suitable finite-difference lattice Boltzmann model is developed and validated against a direct simulation Monte Carlo particle-based method for solving the Enskog equation in curvilinear geometries. The test scenarios include cylindrical Couette and Fourier flow between coaxial cylinders, and spherical Fourier flow between concentric spheres.

This article presents the first ever systematic demonstration of the drag reduction at supersonic speed regime caused by non-rigid surfaces prepared using compliant viscoelastic coating. This work lays the foundation to a new engineering paradigm that fuses engineered surfaces to create positive aerodynamic outcomes at speeds that are relevant to aerial vehicles.

This work studies the rheology of dense granular media, exploring the effects of varying particle size, density, friction and shear profiles across different flow regimes. Utilizing the discrete element method (DEM), the research extends current models by integrating volumetric contributions and introducing a new power-law scaling that unifies local and nonlocal rheology data onto a single master curve. This approach bridges the μ(I)-rheology and Kinetic Theory, offering a framework for predicting the behavior of granular flows in various settings, from geophysical flows to industrial processes.

Dendrite formation resulting from morphological instability in cathodic electrodeposition of a metal and, especially, the role that related fluid flows play, has long been of major interest to physicists. We focus on the physical mechanisms behind: (1) Underlimiting currents: Selection of electrokinetic-reactive length scale, which is the geometric average of the electric double layer width and the reaction-diffusion length defined as the ratio of cation diffusivity to electrode reaction rate; (2) Overlimiting currents: Domination of emerging electroconvective flow, selecting the cathodic diffusion layer width as dominant length scale for morphological instability and emerging dendrites.

We present a self-similarity analysis of single-point turbulent statistics across different quadrants in turbulent wakes. We show here that within the wake self-similar region, the distribution of the Reynolds shear stress in different quadrants can also attain a state of self-similarity. The length scaling is the same for the Reynolds shear stress and its different quadrant contributions, while there exists a difference in velocity scaling. There exists a strong connection between ejection events and large-scale coherent structures, as well as deceleration extreme events.

Wall modes and bulk modes compete in small-aspect-ratio rapidly rotating Rayleigh-Bénard convection. Wall modes remain robust in the presence of bulk convection and contribute substantially to the global heat transport.

Numerical simulations of wet particles often use the particle roughness as a minimum separation criterion to limit the viscous force. Here we investigate the validity of this through a comparison of experiments of binary wet particle collisions to numerical discrete element method (DEM) and smoothed particle hydrodynamics (SPH) simulations.

In this paper, we investigate the exit dynamics of a sphere launched underneath a liquid bath surface at a prescribed impact velocity. Spheres with radii approximate or smaller than the capillary length are considered. The process can be sequenced into a partial exit stage that forms a coated layer, and a full exit stage with an attached ligament. A bouncing-off regime, a lower pinch-off penetration regime, and an upper pinch-off penetration regime are identified, separating by a penetration Weber number and a switching Weber number. The phase diagram is revealed, where the two critical Weber numbers are functions of the Bond number.

We integrated theoretical analysis and numerical simulations to investigate the turbulence transition through a crossflow instability in the boundary layer of a cooler rotating disk within a rotor-stator cavity, influenced by a temperature gradient. This gradient induces centrifugal buoyancy forces that alter the radial inflection points in the mean flow. These changes lead to premature bifurcation of spiral waves, crucial in the transition process, resulting in an early onset of turbulence in the boundary layer of the rotating disk. Our findings underscore the importance of manipulating boundary layer stability via temperature gradients to control turbulent transitions.

To investigate the existence of geometrically self-similar eddies in fully developed turbulent pipe flow, stereoscopic particle image velocimetry measurements were performed in two parallel cross-sectional planes, for friction Reynolds numbers Re${}_{\tau }$ = 1310, 2430, and 3810. The instantaneous turbulence structures are sorted by width using an azimuthal Fourier decomposition, then azimuthally aligned to create a set of average eddy velocity profiles. The streamwise similarity is investigated using two-point correlations. Over the range of scales examined, the candidate structures establish full three-dimensional geometric self-similarity.

We present a numerical study of a thin elastic sheet with small extensibility sedimenting in a viscous fluid in free space or near a wall. The interplay between gravity and the elastic response of sheets gives rise to complex deformation and reorientation dynamics. Near a vertical wall, sheets exhibit asymmetric conformations that cause the sheet to drift toward or away from the wall. Near an inclined wall, sheets show qualitatively different dynamics when the wall angle is large: they either deposit on or slide along the wall with a fixed wall-normal distance.

The dynamics of a free object in an active nematic suspension in a circular container are simulated. For ranges of parameters, unstable chaotic wanderings eventually reach either a fixed-point or limit-cycle (shown) behavior. These flows are analyzed, and similar behaviors confirmed to also occur in more complex geometries.

Scraping of a thin layer of viscoplastic fluid from a horizontal surface by a translating rigid scraper generates a mound of fluid upstream of the scraper and a residual layer behind it. We compute numerical solutions for the system modeled via viscoplastic shallow-layer theory. The unsteady dynamics of this system exhibit a variety of self-similar regimes, for which we construct solutions explicitly and identify key scalings for the temporal development of the mound. We further report experimental results, which are compared with predictions from the shallow-layer theory, obtaining reasonable agreement once a slip boundary condition is included in the model.

We examine the influence of wind forcing on the inception of breaking in surface gravity waves using an ensemble of high-resolution numerical simulations. We find that there is a critical point in the energetic evolution of the wave in which the convergence of kinetic energy at the wave crest can no longer be offset by conversion to potential energy, resulting in a rapid growth of kinetic energy up to breaking onset. This energetic signature is shown to consistently differentiate between non-breaking and breaking waves under a range of wind forcing speeds.

Liquid infused surfaces (LISs) are a nature-inspired surface technology that demonstrates multiple functionalities under laminar and controlled flow conditions. We study experimentally the behavior of the infused lubricant under submerged conditions and turbulent flow. When exposed to turbulence, the lubricant layer develops into a pattern of droplets, the length of which depends on the balance between shear and contact force. The stability of the droplets prevents complete drainage of the lubricant and increases the robustness of the LIS in the presence of turbulence. We identify a model that predicts the equilibrium length of the droplets and validate it with numerical simulations.

APS has selected 156 Outstanding Referees for 2024 who have demonstrated exceptional work in the assessment of manuscripts published in the Physical Review journals. A full list of the Outstanding Referees is available online.

The recipients of the 40th François Naftali Frenkiel Award for Fluid Mechanics are Aliénor Rivière, Daniel J. Ruth, Wouter Mostert, Luc Deike, and Stéphane Perrard for their paper “Capillary driven fragmentation of large gas bubbles in turbulence” which was published in Physical Review Fluids 7, 083602 (2022).

Physical Review Fluids publishes a collection of papers associated with the 2022 Gallery of Fluid Motion. These award winning works were presented at the annual meeting of the APS Division of Fluid Dynamics.

See the 2022 Gallery for the original entries.

The 75th Annual Meeting of the American Physical Society (APS) − Division of Fluid Mechanics was held in Indianapolis, IN from November 20–22, 2022.

The Collection is based on presentations at the 2022 meeting of the APS Division of Fluid Dynamics in Indianapolis, Indiana. Each year the editors of Physical Review Fluids invite the authors of selected presentations made at the Annual meeting of the APS Division of Fluid Dynamics to submit a paper based on their talk to the journal. The selections are made based on the importance and interest of the talk and the submitted papers are peer reviewed. The current set of invited papers is based on presentations made at the 75th Annual meeting of the APS Division of Fluid Dynamics in November 2022. The papers may contain both original research as well as a perspective on the field they cover.

The Editors of Physical Review Fluids highlight the journal’s achievements, its editorial standards, and its special relationship with the APS Division of Fluid Dynamics (DFD).

Beverley McKeon and Eric Lauga describe their vision as new Co-Lead Editors for Physical Review Fluids, which celebrates its fifth anniversary this year.