Physical Review Fluids

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Updated: 23 hours 59 min ago

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

Salt comets in hand sanitizer: A simple probe of microgel collapse dynamics

Thu, 06/06/2019 - 11:00

Author(s): Arash Nowbahar, Art O'Connor, Vincent Mansard, Patrick Spicer, and Todd M. Squires

A single grain of salt, placed on the surface of everyday hand sanitizer, slowly bores a hole through it, leaving a milky “comet trail” in its wake. The fall speed does not depend on the size of the salt grain, but does depend on salt type, and reveals subtle aspects of collapsing microgels.


[Phys. Rev. Fluids 4, 061301(R)] Published Thu Jun 06, 2019

Regularized Stokeslet rings: An efficient method for axisymmetric Stokes flow with application to the growing pollen tube

Thu, 06/06/2019 - 11:00

Author(s): J. Tyrrell, D. J. Smith, and R. J. Dyson

The “regularized ringlet,” which is the fundamental solution to axisymmetric Stokes flow driven by a ring of smoothed point forces, is derived and used to model cytosolic flow in the growing pollen tube.


[Phys. Rev. Fluids 4, 063102] Published Thu Jun 06, 2019

Resolvent-based modeling of coherent wave packets in a turbulent jet

Thu, 06/06/2019 - 11:00

Author(s): Lutz Lesshafft, Onofrio Semeraro, Vincent Jaunet, André V. G. Cavalieri, and Peter Jordan

Linear instability analysis, performed on the mean flow of a fully turbulent jet, provides quantitatively correct predictions of the energetic coherent turbulent structures found in experiments. It is concluded that the most energetic structures in jet turbulence are governed by linear dynamics.


[Phys. Rev. Fluids 4, 063901] Published Thu Jun 06, 2019

Self-similar and disordered front propagation in a radial Hele-Shaw channel with time-varying cell depth

Thu, 06/06/2019 - 11:00

Author(s): C. Vaquero-Stainer, M. Heil, A. Juel, and D. Pihler-Puzović

An air bubble expanding into a viscous liquid in the small gap between parallel plates deforms into highly branched, continuously evolving interfacial fingering patterns. By separating the plates following a power law in time, it is found that the interface can also form self-similar fingering patterns.


[Phys. Rev. Fluids 4, 064002] Published Thu Jun 06, 2019

Self-organization in purely viscous non-Newtonian turbulence

Thu, 06/06/2019 - 11:00

Author(s): H. J. Seybold, H. A. Carmona, H. J. Herrmann, and J. S. Andrade, Jr.

Snapshot of vortex structure in a shear-thickening fluid in fully developed turbulence. Colors from blue to red go from low to high vorticities. Relative to Newtonian fluids, shear-thinning fluids adjust to have an augmented dissipation inside vortices, the opposite of shear-thickening fluids.


[Phys. Rev. Fluids 4, 064604] Published Thu Jun 06, 2019

Lagrangian description of the unsteady flow induced by a single pulse of a jellyfish

Thu, 06/06/2019 - 11:00

Author(s): Jin-Tae Kim and Leonardo P. Chamorro

Lagrangian statistics and pair dispersion induced by an isolated pulse of a small jellyfish are quantified with 3D particle tracking velocimetry. Lagrangian velocity shows more intense mixing in the radial direction and reveals three stages dominated by flow acceleration, mixing, and dissipation.


[Phys. Rev. Fluids 4, 064605] Published Thu Jun 06, 2019

Investigation of shear rates of rolling adhesion on leukocytes with bending of microvilli

Wed, 06/05/2019 - 11:00

Author(s): Tai-Hsien Wu and Dewei Qi

A leukocyte model is used to show how different flow shear rates affect bending deformation of the microvilli and adhesive bond forces.


[Phys. Rev. Fluids 4, 063101] Published Wed Jun 05, 2019

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