Physical Review Fluids

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Flow structure and unsteadiness in a highly confined shock-wave–boundary-layer interaction

Fri, 02/08/2019 - 10:00

Author(s): Jonathan Poggie and Kevin M. Porter

High-fidelity simulations show that the confining effect of sidewalls on a shock-wave/boundary-layer interaction can have a very strong influence on both the mean flow and large-scale unsteadiness, and accurately capturing the sidewall flows is essential in realistic modeling of confined flows.

[Phys. Rev. Fluids 4, 024602] Published Fri Feb 08, 2019

Characterizing vortex tangle properties in steady-state He II counterflow using particle tracking velocimetry

Thu, 02/07/2019 - 10:00

Author(s): Brian Mastracci and Wei Guo

The utility of particle tracking velocimetry for characterizing the quantized vortex tangle in He II thermal counterflow is shown by demonstrating measurements of vortex line spacing, the parameter c2, and vortex reconnection.

[Phys. Rev. Fluids 4, 023301] Published Thu Feb 07, 2019

Application of a self-organizing map to identify the turbulent-boundary-layer interface in a transitional flow

Thu, 02/07/2019 - 10:00

Author(s): Zhao Wu, Jin Lee, Charles Meneveau, and Tamer Zaki

We use the self-organizing map, an unsupervised machine learning method, to find the turbulent/nonturbulent interface in a transitional boundary layer with the help of Johns Hopkins Turbulence Databases. This method separates turbulent regions from vortical streaks and free-stream turbulence.

[Phys. Rev. Fluids 4, 023902] Published Thu Feb 07, 2019

Aerodynamically driven motion of a wall-bounded drop on a smooth solid substrate

Thu, 02/07/2019 - 10:00

Author(s): Patrick M. Seiler, Mark Gloerfeld, Ilia V. Roisman, and Cameron Tropea

The motion of wall-bounded drops moving on solid substrates driven by a fully turbulent channel flow is experimentally investigated. A scaling is found to describe the dimensionless drop velocity in terms of a dimensionless flow attack velocity, taking into account the surface wetting properties.

[Phys. Rev. Fluids 4, 024001] Published Thu Feb 07, 2019

Reconnection of vortex tubes with axial flow

Thu, 02/07/2019 - 10:00

Author(s): P. McGavin and D. I. Pontin

Reconnection of vortex tubes containing twisted vortex lines is studied by numerical simulation, showing that both the sense and strength of the twist affect the topological and geometrical properties of the resulting vortex structures, as well as the timing and rate of the reconnection process.

[Phys. Rev. Fluids 4, 024701] Published Thu Feb 07, 2019

Finite-size Lagrangian coherent structures in a two-sided lid-driven cavity

Wed, 02/06/2019 - 10:00

Author(s): Francesco Romanò, Parvathy Kunchi Kannan, and Hendrik C. Kuhlmann

Finite-size Lagrangian coherent structures can arise in dilute suspensions solely because of the size of the particles. When moving near boundaries, a lubrication-induced drag transfers the particles from the chaotic sea of the unperturbed fluid flow to particular Kolmogorov-Arnold-Moser tori.

[Phys. Rev. Fluids 4, 024302] Published Wed Feb 06, 2019

Fast, thin jets from bubbles expanding and collapsing in extreme vicinity to a solid boundary: A numerical study

Tue, 02/05/2019 - 10:00

Author(s): Christiane Lechner, Werner Lauterborn, Max Koch, and Robert Mettin

Numerical solutions of the compressible Navier-Stokes equation for a bubble collapsing close to a solid boundary find a very thin jet with velocities of 1000m/s.

[Phys. Rev. Fluids 4, 021601(R)] Published Tue Feb 05, 2019

Direct assessment of Kolmogorov's first refined similarity hypothesis

Tue, 02/05/2019 - 10:00

Author(s): John M. Lawson, Eberhard Bodenschatz, Anna N. Knutsen, James R. Dawson, and Nicholas A. Worth

Using 3D averages of energy dissipation rather than a surrogate quantity, high-resolution volumetric measurements and numerical simulations show that velocity increments scale with the local dissipation rate as per Kolmogorov’s 1962 refined similarity hypothesis, supporting small-scale universality.

[Phys. Rev. Fluids 4, 022601(R)] Published Tue Feb 05, 2019

Inertial self-propulsion of spherical microswimmers by rotation-translation coupling

Tue, 02/05/2019 - 10:00

Author(s): Itzhak Fouxon and Yizhar Or

We study inertial spherical squirmers prescribing tangential surface deformations. Breaking axial symmetry induces rotation-translation coupling that overcomes the “scallop theorem”, giving net motion for time-reversible strokes. This swimming mechanism may be relevant for large Volvox colonies.

[Phys. Rev. Fluids 4, 023101] Published Tue Feb 05, 2019

Temperature fluctuations relevant to thermal-plume dynamics in turbulent rotating Rayleigh-Bénard convection

Mon, 02/04/2019 - 10:00

Author(s): Shan-Shan Ding, Hui-Min Li, Wen-Dan Yan, and Jin-Qiang Zhong

Experiments in turbulent rotating Rayleigh-Bénard convection find various statistical properties of the fluctuations of the temperature which can be fit with a model.

[Phys. Rev. Fluids 4, 023501] Published Mon Feb 04, 2019

Cessation of a dense granular flow down an inclined plane

Mon, 02/04/2019 - 10:00

Author(s): S. Bharathraj and V. Kumaran

A simulation study of a dense granular inclined plane flow reveals a sharp transition between a Bagnold flow and a layered flow at critical angle, which is a fraction of a degree above the cessation angle. The layered flow exhibits intriguing features, such as oscillations of the flow velocity.

[Phys. Rev. Fluids 4, 024301] Published Mon Feb 04, 2019

Modeling mode interactions in boundary layer flows via the parabolized Floquet equations

Fri, 02/01/2019 - 10:00

Author(s): Wei Ran, Armin Zare, M. J. Philipp Hack, and Mihailo R. Jovanović

Multimodal stability analysis and parabolization are combined to account for dominant mode interactions in pretransitional flow. A sequence of linear progressions of the resulting parabolized Floquet equations captures disturbance growth and provides excellent agreement with direct numerical simulation results.

[Phys. Rev. Fluids 4, 023901] Published Fri Feb 01, 2019

Three-wave resonant interactions and zonal flows in two-dimensional Rossby-Haurwitz wave turbulence on a rotating sphere

Fri, 02/01/2019 - 10:00

Author(s): Kiori Obuse and Michio Yamada

The importance of zonal modes in discussing three-wave resonant nonlinear interactions in two-dimensional turbulence on a rotating sphere is investigated. Zonal modes should not be ignored although the energy exchanges between zonal and nonzonal modes by resonant interactions are not possible.

[Phys. Rev. Fluids 4, 024601] Published Fri Feb 01, 2019

Editorial: The 2018 François Naftali Frenkiel Award for Fluid Mechanics

Thu, 01/31/2019 - 10:00

Author(s): John Kim and Gary Leal

[Phys. Rev. Fluids 4, 010002] Published Thu Jan 31, 2019

Mode selection on breakup of a droplet falling into a miscible solution

Wed, 01/30/2019 - 10:00

Author(s): Michiko Shimokawa and Hidetusgu Sakaguchi

A study of the breakup of a droplet falling into a miscible solution of lower density shows that a nondimensional parameter determines the breakup number. A mechanism of the mode-selection based on the Rayleigh-Taylor instability for the growing vortex ring is discussed.

[Phys. Rev. Fluids 4, 013603] Published Wed Jan 30, 2019

Linear and nonlinear stability of a quasigeostrophic mixing layer subject to a uniform background shear

Wed, 01/30/2019 - 10:00

Author(s): Luca Biancofiore and Orkan M. Umurhan

The stability of a quasigeostrophic mixing layer is revisited from the kernel wave perspective with a focus on individual Rossby waves behavior. We further conduct nonlinear simulations which show how vortex pairing is hindered by introducing an adverse shear or a finite Rossby radius.

[Phys. Rev. Fluids 4, 013803] Published Wed Jan 30, 2019

Vertical dispersion of Lagrangian tracers in fully developed stably stratified turbulence

Tue, 01/29/2019 - 10:00

Author(s): N. E. Sujovolsky and P. D. Mininni

We put forth a model that captures the vertical single- and two-particle dispersion in stably stratified turbulence. The model gives insight into the mixture of linear and nonlinear physics in these flows, and on the different physical processes responsible for vertical turbulent dispersion.

[Phys. Rev. Fluids 4, 014503] Published Tue Jan 29, 2019

Torsional solutions of convection in rotating fluid spheres

Fri, 01/25/2019 - 10:00

Author(s): J. Sánchez Umbría and M. Net

A numerical study of the nonlinear torsional solutions of convection in rotating, internally heated, self-gravitating fluid spheres shows a sequence of transitions towards chaos in which heteroclinic chains connecting unstable periodic solutions can be recognized.

[Phys. Rev. Fluids 4, 013501] Published Fri Jan 25, 2019

Unstable yet static initial state: A universal method for studying Rayleigh-Taylor instability and lock exchange

Thu, 01/24/2019 - 10:00

Author(s): Kazuya U. Kobayashi and Rei Kurita

An experimental method for investigating hydrodynamic instability combining light and a physical gel is proposed. Our method allows for a detailed study of hydrodynamic instabilities.

[Phys. Rev. Fluids 4, 013901] Published Thu Jan 24, 2019

Hydroelastic wake on a thin elastic sheet floating on water

Thu, 01/24/2019 - 10:00

Author(s): Jean-Christophe Ono-dit-Biot, Miguel Trejo, Elsie Loukiantcheko, Max Lauch, Elie Raphaël, Kari Dalnoki-Veress, and Thomas Salez

The hydroelastic wake created by a perturbation moving along a thin elastic sheet floating atop water is studied. The waves are characterized as a function of the perturbation speed and sheet thickness. Gravity, bending, and stretching are quantified and all are found to be important.

[Phys. Rev. Fluids 4, 014808] Published Thu Jan 24, 2019