Latest papers in fluid mechanics

Author(s): Sandip Dighe, Dilip Kumar Maity, Jeffrey N. Fonnesbeck, Som Dutta, and Tadd Truscott

Most studies of droplet impact on liquid pools focus on droplet diameters up to the capillary length (0.27 cm). We break from convention and study extremely large water droplets (1 to 6 cm diameter) falling into a pool of water. We demonstrate that the depth and width of the cavity formed by large d…

[Phys. Rev. E 109, 045107] Published Tue Apr 16, 2024

Author(s): L. Moriconi, R. M. Pereira, and V. J. Valadão

We carry out an in-depth analysis of a recently introduced vortex gas model of homogeneous and isotropic turbulence. Direct numerical simulations are used to provide a concrete physical interpretation of one of the model's constituent fields: the degree of vortex polarization. Our investigations she…

[Phys. Rev. E 109, 045106] Published Mon Apr 15, 2024

Author(s): Diego Donzis and Shilpa Sajeev

Turbulent flows comprise a multitude of scales which make them extremely difficult to analyze and simulate. In this work, we study homogeneous isotropic turbulence using a novel approach which solves the Navier-Sokes equations on a reduced set of modes that are sampled stochastically. The complementary set are solved using trivial dynamics. This method, called Selected Eddy Simulations, is able to capture broad dynamics of turbulence with just 10% of resolved modes, suggesting the turbulence attractor may be smaller or more robust to modeling than previously thought. This result also holds promise for developing alternative low-cost numerical approaches to study turbulent flows.

[Phys. Rev. Fluids 9, 044605] Published Mon Apr 15, 2024

Author(s): Alexander Yu. Gelfgat and Gerrit Maik Horstmann

Electrocapillary flows in a classical experiment of Melcher and Taylor are studied. The computed streamlines qualitatively represent the experimental image. With the increase of electrocapillary forcing, the main circulation localizes near a boundary with a larger electric potential. When a dielectric liquid is replaced by a poorly conducting one, the system becomes non-isothermal owing to the Joule heating, and the flow is driven also by buoyancy and thermocapillary convection. The results show that consideration of the two-phase model is mandatory. The Lippmann equation, connecting electrically induced surface tension with nonuniform surface electric potential, is numerically verified.

[Phys. Rev. Fluids 9, 044101] Published Fri Apr 12, 2024

Author(s): Alexander V. Milovanov and Jens Juul Rasmussen

This paper is concerned with the processes of spatial propagation and penetration of turbulence from the regions where it is locally excited into initially laminar regions. The phenomenon has come to be known as “turbulence spreading” and witnessed a renewed attention in the literature recently. Her…

[Phys. Rev. E 109, 045105] Published Thu Apr 11, 2024

Author(s): S. Balachandar, C. Peng, and L.-P. Wang

The presence of a dispersed phase substantially modifies small-scale turbulence. Here we present a comprehensive mechanistically based model to predict turbulence modulation, the predictions of which, compared with particle-resolved simulations and experiments, is shown.

[Phys. Rev. Fluids 9, 044304] Published Thu Apr 11, 2024

Author(s): Xiaokang Zhang, Jake Minten, and Bhargav Rallabandi

Acoustic fields are used in numerous applications to induce movement of suspended particles. We develop a rigorous theory that systematically unifies inviscid acoustophoresis with viscous streaming. The theory connects particle motion to a generalized form of the secondary radiation force, which depends on the Stokes layer thickness around the particle, and the contrast of density and compressibility between the particle and the fluid. We identify a reversal of particle motion when inertial and viscous forces are comparable, validated with numerical solutions. This has significant implications for applications involving particle sorting or focusing based on size or material properties.

[Phys. Rev. Fluids 9, 044303] Published Wed Apr 10, 2024

Author(s): Daniele Colognesi, Ubaldo Bafile, Eleonora Guarini, and Martin Neumann

In this paper, we report the results of a centroid molecular dynamics (CMD) study of the canonical velocity autocorrelation functions (VACFs) in liquid Ne−D2 mixtures at a temperature of T=30K and in the full D2-concentration range (0%≤xD2≤100%). This binary system was selected because of its modera…

[Phys. Rev. E 109, 045104] Published Tue Apr 09, 2024

Author(s): Frédéric Alizard, Benoît Pier, and Smail Lebbal

Shear flows in contact with compliant boundaries exhibit a rich dynamics involving traveling-wave-flutter, Tollmien-Schlichting, as well as divergence instabilities. In this context, maximum transient growth effects are the result of optimal energy exchanges during the fluid-structure interaction process. The present investigation studies the detailed contribution of the different interacting modes. In particular, it is found that the optimal gain may be associated with a large-amplitude oscillatory behavior and that wall-compliance enhances this phenomenon.

[Phys. Rev. Fluids 9, 043905] Published Tue Apr 09, 2024

Author(s): Junhong Wu, Daniel Lester, Michael G. Trefry, and Guy Metcalfe

This study focuses on how Lagrangian coherent structures (LCSs) control solute dispersion in heterogeneous poroelastic media (HPM). We show how interactions between medium compressibility, conductivity heterogeneity, and periodic forcing give rise to complex flows and diverse LCS types (KAM islands, chaotic saddles, etc) that have profound impacts on diffusive solute transport (main image) that do not arise in the steady counterpart (inset). Strongly anomalous transport impacts both spatial moments and residence time distributions and persists at low Péclet numbers. This study reveals the complex transport phenomena that can arise in HPM and shows how LCSs govern solute dispersion.

[Phys. Rev. Fluids 9, 044501] Published Tue Apr 09, 2024

Author(s): Bianca Viggiano, Thomas Basset, Mickaël Bourgoin, Raúl Bayoán Cal, Laurent Chevillard, Charles Meneveau, and Romain Volk

We propose a novel approach to accurately model complex flow, ultimately predicting the behavior of a turbulent jet by molding a set of velocity signals input from an idealized flow (readily available from numerical databases online). The model uses fundamental properties of the jet, such as velocity means and standard deviations, easily accessible from textbooks, experiments, or low-order simulations (RANS, LES). The modeled jet reproduces many subtle and intricate properties of the turbulent flow, including the intermittent extreme events known to exist in turbulent flows, which have been typically thought of as not capable of being captured with current modeling techniques.

[Phys. Rev. Fluids 9, 044604] Published Tue Apr 09, 2024

Author(s): Han Wu, Yuhong Li, Xin Zhang, Siyang Zhong, and Xun Huang

In this work, we experimentally investigate turbulence ingesting rotor noise under various thrusting states. The broadband noise caused by turbulence ingestion is found to dominate at the normalized frequency range of fR/U∞ = 20 to 80 when the rotor is under low-thrusting conditions. Results also suggest that the turbulence ingestion broadband noise can be scaled by Mach number scaling of M∞2Mc4, where M∞ is the freestream Mach number, and Mc is the corresponding blade tip Mach number.

[Phys. Rev. Fluids 9, 044801] Published Tue Apr 09, 2024

Author(s): Whitney T. Powers, Evan H. Anders, and Benjamin P. Brown

In stars and planets natural processes heat convective flows in the bulk of a convective region rather than at hard boundaries. Internally heated convection has been studied extensively in incompressible fluids, but the effects of stratification and compressibility have not been examined in detail. In this work, we study fully compressible convection driven by a spatially uniform heating source in a suite of two- and three-dimensional Cartesian, hydrodynamic simulations. We characterize how Mach, Reynolds, and Nusselt numbers scale with the characteristic strength of the internal heat source. We also measure kinetic energy power spectra and discuss the flow morphologies.

[Phys. Rev. Fluids 9, 043501] Published Tue Apr 09, 2024

Author(s): J. Simon Kern, Valerio Lupi, and Dan S. Henningson

Unsteady flows in curved pipes are ubiquitous in science and engineering but their stability characteristics are not well understood in most cases of practical interest. We study the linear stability of pulsatile flow in the archetypal configuration of a toroidal pipe, which appears e.g. in aortic blood flow. The Floquet stability analysis of the harmonically forced system reveals that the curvature leads to nonlinear interactions in the baseflow andconsiderable stabilization that can be orders of magnitude larger than in the corresponding planar case. The figure shows a typical snapshot of the streamwise velocity field in a torus subject to a pulsating pressure gradient.

[Phys. Rev. Fluids 9, 043906] Published Tue Apr 09, 2024

Author(s): Runfeng Zhou, Mathew M. Swisher, Akshay Deshmukh, Chengzhen Sun, John H. Lienhard, and Nicolas G. Hadjiconstantinou

We develop a model that describes the permeance of simple fluids as well as small hydrocarbon molecules through nanoporous, atomically thin membranes. The model is in agreement with molecular dynamics simulations for a wide range of pore sizes, including pores approaching the steric exclusion limit, as needed for understanding separation processes using such membranes.

[Phys. Rev. Fluids 9, 044202] Published Tue Apr 09, 2024

Author(s): Hai-Tao Zhu, Long Chen, and Ming-Jiu Ni

This numerical simulation investigates the vertical convection of liquid metal with varying magnetic fields and wall conductivities. The applied horizontal magnetic field alters plume dynamics and topology, leading to a more coherent large-scale flow structure but weakening convection through Joule dissipation. This competition between rectification and magnetic damping determines the magnetic field’s impact on heat transfer, with the quasi-two-dimensional state being the threshold. Our analysis demonstrates that while the plume area remains constant, condensation of coherent structures enhances horizontal heat transport per unit area, significantly improving overall heat transfer.

[Phys. Rev. Fluids 9, 043701] Published Mon Apr 08, 2024

Author(s): Zhibo Li, Clément Bielinski, Anke Lindner, Olivia du Roure, and Blaise Delmotte

We combine experiments and numerical simulations to investigate the interaction between a rigid fiber and a triangular obstacle in a microfluidic channel. We find different dynamics depending on the initial position and orientation of the fiber. We show that these dynamics are dictated by the fiber configuration in the vicinity of the obstacle. Some dynamics induce a cross-stream migration which grows with the fiber length. Our findings could in the future be used to design and optimize microfluidic sorting devices to sort rigid fibers by length.

[Phys. Rev. Fluids 9, 044302] Published Mon Apr 08, 2024