Electroconvection (EC) turbulence is an important branch of electrohydrodynamics (EHD). This work applies large-eddy simulation (LES) to EHD turbulence based on the lattice Boltzmann method. The Smagorinsky and WALE models are used for the momentum equation, and the turbulent Schmidt number models the charge transport equation. The results are compared with those computed through different numerical models. Both two-dimensional and three-dimensional numerical tests show that the LES models applied in EHD turbulence simulation perform reliable results at high computational speed, making them suitable for further simulations of EHD turbulence.

We investigate an ice block melting in a box and reveal that the aspect ratio and ambient temperature play a crucial role in the melting process, leading to substantial variations in melt rates and shape evolution. In general, the shape which melts the slowest is quite distinct from that of a disk, due to the symmetry breaking by buoyancy-driven thermal convection. Predicting their melting rates is crucial for understanding the interplay between melting icebergs with the climate.

Beyond a threshold speed, the receding contact line of a partially wetting liquid on a solid substrate becomes unstable, forming a corner. At these speeds, one expects the inertial effects near the contact line to be significant for many liquids commonly used in industrial processes. To account for it, we provide the self-similar leading-order inertial correction to the well-known Stokes solution for the interface shape and flow field near the moving contact line. Furthermore, inspired by recent experiments, we make quantitative predictions for water and liquid mercury and argue that it is essential to consider inertial contributions when modeling fast-moving contact lines.

Carotid artery disease is a significant contributor to mortality in the United States. The role of internal vortical structures in enhancing pro-atherosclerotic wall shear stresses and how they differ between healthy and disease-prone patient cohorts has not been studied. This study revealed an important vortex which forms in the cardiac cycle at a time primarily dictated by bifurcation geometry, whereas its lifespan is determined by flow conditions, such as pressure drop and flow rate. We found that high internal carotid artery mass flow rate and a high favorable pressure gradient maximum occurring near peak systole are strong indicators of a greater pre-disposition towards atherogenesis.

This study proposes a machine-learning solution to address the log-layer mismatch problem that occurs when the erroneous near-wall flow variables are used as the input for the wall model in a wall-modeled large eddy simulation. Neural networks are employed to correct the errors in the near-wall flow variables before they are used as the input for the wall model. The input and output features of the neural networks are selected based on the physical relations of the turbulent boundary layer for robustness against various Reynolds and Mach number conditions. The proposed neural networks enable the wall model to accurately predict the wall shear stress and the resultant turbulence statistics.

Baroclinic instability plays an important role in rotating stratified fluid systems, such as Earth’s atmosphere and ocean, and can be modeled as a pair of constructively interfering edge-waves. We provide a self-consistent explanation of how the edge-wave interaction mechanism is modified in the presence of slopes, extending existing simple but incomplete explanations. We also put forth speculations on using linear instability theory to inform eddy parameterizations, and highlight parity-time symmetry in the governing equations, finding links between shear instabilities, interacting edge-waves, eddy-mean interactions, and concepts from quantum field theory.

Turbulence is ubiquitous in our world, attributed to diverse mechanisms that may act alone or together. Traditionally, inspired by the reductionist approach, the dominant turbulence-inducing mechanism has been isolated and minor ones neglected. However, are the minor factors truly negligible? Recent research, grounded in conservation of kinetic energy and multicomponent scalar variance fluxes, suggests otherwise. Even weaker mechanisms, such as electric body forces, can significantly influence the cascades of turbulence in the presence of a dominant mechanism like buoyancy-driven turbulence, leading to the emergence of new scaling indices and diverse observations in real-world turbulence.

Impulsively generated focused jets play significant roles in advanced manufacturing and biomedical applications, where the viscous effects are crucial in jet dynamics. In this study, we find that mass and momentum transfer along the tangential direction of the free surface contribute to focused jet formation. The viscosity-induced diffusion of the shear flow and vorticity near the free surface reduces the jet speed. These findings offer new perspectives on viscous interface dynamics.

The presented methodology fuses computational models with experimental data to enhance the Spalart-Allmaras (SA) turbulence model for Reynolds-averaged Navier-Stokes equations. By leveraging the Ensemble Kalman filtering approach (EnKF), this study refines the SA model’s coefficients, ensuring improved performance on separated flows without any accuracy trade-off on flows already well captured by SA. Validated on different flow conditions, including a backward-facing step and a NASA wall-mounted hump, the recalibrated model demonstrates significant improvements in key metrics.

This study investigates the key stages before aerosol formation by bursting bubbles: capillary wave propagation, convergence at the bubble apex, Worthington jet ascent, and droplet release. We focus on overlooked factors: surface-active agents and gravitational effects, quantified by the Bond number. Our results propose a new mechanism explaining capillary wave retardation in surfactants, involving the transition from bi- to uni-directional Marangoni stresses, which counter wave motion. We also elucidate the varying wave velocities with different surfactant properties, challenging the constant velocity observed in clean interfaces.

The reason for the deviation of measured generalized Townsend-Perry (T-P) constants from the previous Gaussian prediction based on the attached eddy model is found and the universal expression of the generalized T-P constants, regardless of the eddy type, is derived. These findings may contribute further insight into the fundamental statistical characteristics of coherent motions in flow fields and provide good indications for testing the accuracy of numerical simulations in high-Reynolds-number flows.

We study the role played by upstream-traveling guided waves on the generation of tones by a supersonic, ideally-expanded round jet impinging on a flat plate. We explore a finite-thickness stability model for the prediction of allowable frequency ranges for resonance based on the dynamics of such waves. We show that the frequency ranges predicted by the finite-thickness model are consistent with the vast majority of experimental and numerical data available in the literature, correcting discrepancies observed previously with vortex sheet models. This provides further evidence for the involvement of guided jet modes in the resonance mechanism.

Viscoelastic fluids may exhibit complex flow behaviors, such as nontrivial normal stress differences and time-dependent responses, which can significantly impact the settling dynamics of suspended particles. We investigate particle-wall interactions for the case of a sphere moving close to and normal to a wall in an Oldroyd-B fluid, considering both prescribed velocity and force scenarios; the lubrication approximation and Deborah number perturbation techniques are used.

We present a theoretical model for viscous liquid systems exhibiting Rayleigh-Plateau instability, considering cases with and without a solid fiber. Using the lubrication approach and hydrodynamic interactions at the solid-liquid interface, we derive one-dimensional evolution equations for the breakup of viscous liquid threads and films on fibers. Our model aligns well with experimental results, unifying Goren’s liquid film on a fiber and Rayleigh’s viscous liquid thread findings. It identifies the most unstable mode as proportional to the wavenumber quadratically and reveals the exponential decay of satellite droplet volume with increasing wavenumber.

Cohesive force chain networks during a granular collapse process. Such networks can be identified by means of community detection approaches.

Droplet impacting on rotating surface experiences the tangential shear force from the rotating surface, generating a centrifugal force that either enhances the spreading or destabilizes the expanding lamella. In this study, we experimentally characterize the impacting of droplets with a wide range of viscosity on rotating surfaces with various wettabilities, and theoretically analyze the observed impacting dynamics, including the enhanced spreading and the transition to the destabilization of the expanding lamella. We propose a simplified approach to predict these key parameters, and validate the theoretical prediction by experimental measurement.

Permafrost thaw plays a crucial role in climate change dynamics, yet the intricate small-scale processes driving thawing remain inadequately understood. Here we reveal that the density anomaly of water has the potential to trigger convection in coarse-grained soils above permafrost. By using high-resolution numerical simulations of the primitive equations in porous media we show that convection significantly accelerates the thawing process. Climate models that predominantly account for thawing induced by diffusive processes alone overlook this aspect, which can self-reinforce and lead to enhanced climate-permafrost feedback.

The dynamics of flexible filaments entrained in flow are important for understanding many biological and industrial processes. This work describes a data-driven technique to create high-fidelity low-dimensional models of flexible fiber dynamics using machine learning; the technique is applied to sedimentation in a quiescent, viscous Newtonian fluid, using results from detailed simulations as the data set. Over a wide range of fiber flexibilities, the filament shape dynamics can be represented with high accuracy with only four degrees of freedom.

The policy requires authors to explain where research data can be found starting Sept. 4.

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

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.