Physical Review Fluids

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Small-scale flow topologies in decaying isotropic turbulence laden with finite-size droplets

Thu, 06/13/2019 - 11:00

Author(s): Michael S. Dodd and Lluís Jofre

The small-scale flow topologies in droplet-resolved direct numerical simulations of isotropic turbulence are classified using tensor invariants. The results show that when approaching the droplet surface, the flow topologies fundamentally change from those found in isotropic turbulence to boundary-layer-like structures.

[Phys. Rev. Fluids 4, 064303] Published Thu Jun 13, 2019

Frozen waves in turbulent mixing layers

Thu, 06/13/2019 - 11:00

Author(s): Benoît-Joseph Gréa and Antoine Briard

The horizontal vibrations of an interface between miscible fluids trigger a parametric instability, leading to frozen wave patterns. Theory and numerical simulations reveal that the mixing layer size varies as the square of the forcing amplitude in the turbulent regime.

[Phys. Rev. Fluids 4, 064608] Published Thu Jun 13, 2019

Strong turbulence for vibrating plates: Emergence of a Kolmogorov spectrum

Thu, 06/13/2019 - 11:00

Author(s): Gustavo Düring, Christophe Josserand, Giorgio Krstulovic, and Sergio Rica

In the low viscosity liquid and zero thickness vibrating elastic sheet, turbulent behavior is observed. We find the same Kolmogorov spectrum cascade for energy redistribution per scale Ek∼P2/3k−5/3 in both, apparently, completely disparate physical situations.

[Phys. Rev. Fluids 4, 064804] Published Thu Jun 13, 2019

Vectorial structure of the near-wall premixed flame

Wed, 06/12/2019 - 11:00

Author(s): Peipei Zhao, Lipo Wang, and Nilanjan Chakraborty

A turbulent premixed flame anchored by a solid wall can reach a statistically stationary state. Overall the configuration is counterflowlike. Flame-wall interactions under such conditions are key to understanding combustion in a confined space and in developing wall flame models. A numerical study is presented.

[Phys. Rev. Fluids 4, 063203] Published Wed Jun 12, 2019

Turning strategies for plunging elastic plate propulsor

Wed, 06/12/2019 - 11:00

Author(s): Peter D. Yeh, Ersan Demirer, and Alexander Alexeev

Complex actuation of a caudal fin can generate turning moments enabling underwater swimmer navigation. A numerical study explores the hydrodynamics resulting from two actuation strategies leading to pitching and yaw moments.

[Phys. Rev. Fluids 4, 064101] Published Wed Jun 12, 2019

Inertial effects on the dynamics of rigid heavy fibers in isotropic turbulence

Wed, 06/12/2019 - 11:00

Author(s): Sofia Kuperman, Lilach Sabban, and René van Hout

Holographic cinematography is used to measure rotational and translational dynamics of inertial fibers in isotropic turbulence. Results show that for the present parameter range, translational motion is similar to that for spheres. In contrast, tumbling rates peaked at an intermediate Stokes number.

[Phys. Rev. Fluids 4, 064301] Published Wed Jun 12, 2019

Quantitative study of the rheology of frictional suspensions: Influence of friction coefficient in a large range of viscous numbers

Wed, 06/12/2019 - 11:00

Author(s): William Chèvremont, Bruno Chareyre, and Hugues Bodiguel

A numerical study of sheared suspensions of frictional and frictionless rigid spheres finds that macroscopic friction in granular suspensions is nearly independent of interparticle contact friction, and besides contact lubrication, the viscous contribution of the pore fluid is negligibly small.

[Phys. Rev. Fluids 4, 064302] Published Wed Jun 12, 2019

Evolution of a line vortex in stratified flow

Wed, 06/12/2019 - 11:00

Author(s): Surupa Shaw and John P. McHugh

A pair of distributed vortices in stratified flow disintegrate sooner than a traditional vortex pair and form multiple coherent vortex structures.

[Phys. Rev. Fluids 4, 064803] Published Wed Jun 12, 2019

Analysis of nonequidiffusive premixed flames in obstructed channels

Tue, 06/11/2019 - 11:00

Author(s): Abdulafeez Adebiyi, Olatunde Abidakun, Gbolahan Idowu, Damir Valiev, and V’yacheslav Akkerman

The impact of the Lewis number on ultrafast premixed flame acceleration in channels equipped with comb-shaped arrays of tightly spaced obstacles attached to the walls is studied by the computational simulations of the reacting flow equations, including fully compressible hydrodynamics.

[Phys. Rev. Fluids 4, 063201] Published Tue Jun 11, 2019

Unresolved stress tensor modeling in turbulent premixed V-flames using iterative deconvolution: An <i>a priori</i> assessment

Tue, 06/11/2019 - 11:00

Author(s): Z. M. Nikolaou, Y. Minamoto, and L. Vervisch

The application of an iterative deconvolution modeling framework for the unresolved stresses in turbulent and reacting flows is demonstrated using high-fidelity direct numerical simulation data of premixed rod-stabilized V-flames.

[Phys. Rev. Fluids 4, 063202] Published Tue Jun 11, 2019

Influence of a small amount of noncondensable gas on shock wave generation inside a collapsing vapor bubble

Tue, 06/11/2019 - 11:00

Author(s): Kyohei Yamamoto, Kazumichi Kobayashi, Masao Watanabe, Hiroyuki Fujii, Misaki Kon, and Hiroyuki Takahira

A numerical study of the collapse of a vapor bubble finds that a small amount of noncondensable molecules affects the temperature profile inside the collapsing vapor bubble, preventing shock wave generation inside the collapsing bubble.

[Phys. Rev. Fluids 4, 063603] Published Tue Jun 11, 2019

Vortex merging in a laminar separation bubble under natural and forced conditions

Tue, 06/11/2019 - 11:00

Author(s): J. W. Kurelek, S. Yarusevych, and M. Kotsonis

Experiments find that vortex merging occurs naturally in a laminar separation bubble. Acoustic forcing at the subharmonic and fundamental vortex shedding frequency promotes and inhibits merging, respectively. In all cases, merging occurs in the aft portion of the bubble in a spanwise nonuniform manner.

[Phys. Rev. Fluids 4, 063903] Published Tue Jun 11, 2019

Pancake making and surface coating: Optimal control of a gravity-driven liquid film

Tue, 06/11/2019 - 11:00

Author(s): E. Boujo and M. Sellier

Imagine a thin liquid film that must cover the substrate it spreads over before solidifying: tilting the substrate is useful to get a little push from gravity, but obtaining a uniform film thickness is challenging. Here, an adjoint method finds time-dependent motions that improve uniformity.

[Phys. Rev. Fluids 4, 064802] Published Tue Jun 11, 2019

Lagrangian acceleration timescales in anisotropic turbulence

Mon, 06/10/2019 - 11:00

Author(s): Peter D. Huck, Nathanael Machicoane, and Romain Volk

In a Lagrangian point of view, anisotropy in small time scales of turbulent flow is not yet well understood. Using Particle Tracking Velocimetry over nearly a decade in Taylor-scale based Reynolds numbers, we theoretically predict anisotropic acceleration correlation times of tracer particles in turbulent flow.

[Phys. Rev. Fluids 4, 064606] Published Mon Jun 10, 2019

Kinetic energy budget of the largest scales in turbulent pipe flow

Mon, 06/10/2019 - 11:00

Author(s): C. Bauer, A. von Kameke, and C. Wagner

Very-large-scale motions contribute significantly to the kinetic energy in turbulent pipe flow. An analysis of the scale energy budget reveals a similar production mechanism compared to the small scales, but the interscale energy exchange is found to be quite different.

[Phys. Rev. Fluids 4, 064607] Published Mon Jun 10, 2019

Flow and air-entrainment around partially submerged vertical cylinders

Mon, 06/10/2019 - 11:00

Author(s): Valentin Ageorges, Jorge Peixinho, and Gaële Perret

When a partially submerged vertical cylinder is moved at constant speed through water, the motion induces a turbulent wake, free-surface deformations up to the rupture, and air entrainment within the flow. Two modes of air entrainment are uncovered and the critical velocity is compared to a model.

[Phys. Rev. Fluids 4, 064801] Published Mon Jun 10, 2019

Drag coefficient for a sedimenting and rotating sphere in a viscoelastic fluid

Fri, 06/07/2019 - 11:00

Author(s): Alfonso Castillo, William L. Murch, Jonas Einarsson, Baltasar Mena, Eric S. G. Shaqfeh, and Roberto Zenit

The image shows the flow field around a sphere that sediments and rotates simultaneously in a viscoelastic liquid.

[Phys. Rev. Fluids 4, 063302] Published Fri Jun 07, 2019

Anomalous percolation flow transition of yield stress fluids in porous media

Fri, 06/07/2019 - 11:00

Author(s): Nicolas Waisbord, Norbert Stoop, Derek M. Walkama, Jörn Dunkel, and Jeffrey S. Guasto

Microfluidic experiments and simulations reveal an anomalous percolation transition for the flow of a yield stress fluid through a random porous medium. The evolution of the fluidized network results in a highly nonlinear flow conductivity and reveals a novel dispersion mechanism.

[Phys. Rev. Fluids 4, 063303] Published Fri Jun 07, 2019

Computational study of the collapse of a cloud with $12\phantom{\rule{0.16em}{0ex}}500$ gas bubbles in a liquid

Fri, 06/07/2019 - 11:00

Author(s): U. Rasthofer, F. Wermelinger, P. Karnakov, J. Šukys, and P. Koumoutsakos

The collapse of a spherical cloud composed of 12 500 gas bubbles in water is studied. Wave propagation is captured and compared to existing reduced order models. Microjet formation is quantified and a dependence between microjet velocity magnitude and the strength of the collapse wave is identified.

[Phys. Rev. Fluids 4, 063602] Published Fri Jun 07, 2019

Sensitivity of vortex pairing and mixing to initial perturbations in stratified shear flows

Fri, 06/07/2019 - 11:00

Author(s): Wenjing Dong, E. W. Tedford, M. Rahmani, and G. A. Lawrence

An investigation of the phase relationship between the Kelvin-Helmholtz mode and its subharmonic mode finds that it has important implications for vortex pairing and mixing in the flow by ensuring the instability. Results are consistent with laboratory observations for suppression of the subharmonic mode near an unfavorable phase.

[Phys. Rev. Fluids 4, 063902] Published Fri Jun 07, 2019