Physical Review Fluids

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Anomalous wave statistics induced by abrupt depth change

Tue, 01/22/2019 - 10:00

Author(s): C. Tyler Bolles, Kevin Speer, and M. N. J. Moore

A normally-distributed unidirectional wave-field is observed in experiments to become highly skewed and non-Gaussian upon encountering an abrupt change in depth.

[Phys. Rev. Fluids 4, 011801(R)] Published Tue Jan 22, 2019

Experimental comparison of initiation of motion for submerged objects resting on fixed permeable and impermeable beds

Tue, 01/22/2019 - 10:00

Author(s): Heng Wu, Carlo C. Zuniga Zamalloa, Blake J. Landry, and Marcelo H. Garcia

Laboratory experiments suggest a larger Shields parameter value requirement to initiate motion on permeable beds than on impermeable ones, which is connected with the lower lift force on a permeable bed.

[Phys. Rev. Fluids 4, 013802] Published Tue Jan 22, 2019

Three-dimensional flow structures of turbulence in precessing spheroids

Tue, 01/22/2019 - 10:00

Author(s): Ken Komoda and Susumu Goto

Direct numerical simulations reveal the three-dimensional flow structures, sustaining mechanism, and sustainability condition of developed turbulence in precessing spheroids.

[Phys. Rev. Fluids 4, 014603] Published Tue Jan 22, 2019

Waveform of gravity and capillary-gravity waves over a bathymetry

Tue, 01/22/2019 - 10:00

Author(s): Jie Yu

The exact Floquet theory reveals that the waveforms (eigenfunctions) of linear eigenwaves over a variable bed have complex features that are reminiscent of nonlinear waveforms. This is in contrast to the long-standing view that linear time harmonic waves are of permanent sinusoidal form.

[Phys. Rev. Fluids 4, 014806] Published Tue Jan 22, 2019

Observation of alternately localized Faraday waves in a narrow tank

Tue, 01/22/2019 - 10:00

Author(s): Zhigang Zhu, Yalei Song, Xiaonan Liu, Dawu Xiao, Lei Yang, and Liang Huang

We observed in a vibrating rectangular narrow tank a cramped water wave that acts as a sequence of load-carrying beams with one end oscillating and the other end almost pinned to the wall. We find the wave to be composed of just two harmonic waves. Nonlinearities account for this robust structure.

[Phys. Rev. Fluids 4, 014807] Published Tue Jan 22, 2019

Orthogonal liquid-jet impingement on wettability-patterned impermeable substrates

Fri, 01/18/2019 - 10:00

Author(s): Uddalok Sen, Souvick Chatterjee, Julie Crockett, Ranjan Ganguly, Lisha Yu, and Constantine M. Megaridis

A liquid jet striking orthogonally a horizontal superhydrophilic surface can produce a circular hydraulic jump. The same jet impinging on a superhydrophobic surface forms a film that breaks up into droplets. The same superhydrophobic surface with a wettable ring causes a different jet impact outcome.

[Phys. Rev. Fluids 4, 014002] Published Fri Jan 18, 2019

Resolved simulations of sedimenting suspensions of spheres

Fri, 01/18/2019 - 10:00

Author(s): Daniel P. Willen and Andrea Prosperetti

We analyze resolved simulations of up to 2000 spherical particles suspended in an incoming fluid stream with single-particle Reynolds number from 40-110 and volume fraction 9-35%. Diffusivities, pair distributions, and other quantities are found. Tetrads (four particle groups) are also studied.

[Phys. Rev. Fluids 4, 014304] Published Fri Jan 18, 2019

Spontaneous instability in internal solitary-like waves

Thu, 01/17/2019 - 10:00

Author(s): Chengzhu Xu, Marek Stastna, and David Deepwell

The onset and growth of shear instability in internal solitary waves is studied. It is found that there are cases in which the instability occurs spontaneously, cases in which its onset is Reynolds-number dependent, and cases in which it must be triggered by externally imposed noise.

[Phys. Rev. Fluids 4, 014805] Published Thu Jan 17, 2019

Effect of motility on the transport of bacteria populations through a porous medium

Wed, 01/16/2019 - 10:00

Author(s): Adama Creppy, Eric Clément, Carine Douarche, Maria Veronica D'Angelo, and Harold Auradou

An experimental study of the effects of bacterial motility on its transport in a porous medium is presented. For flow velocity that can exceed 10 times the swimming velocity, the transport is found to be strongly retarded by the particle-grain hydrodynamic interaction. This is not observed in nonmotile bacteria.

[Phys. Rev. Fluids 4, 013102] Published Wed Jan 16, 2019

Impact of turbulence on flying insects in tethered and free flight: High-resolution numerical experiments

Wed, 01/16/2019 - 10:00

Author(s): Thomas Engels, Dmitry Kolomenskiy, Kai Schneider, Marie Farge, Fritz-Olaf Lehmann, and Jörn Sesterhenn

We perform high resolution numerical simulations of a bumblebee interacting with a turbulent inflow for both tethered and free flight. We find that average aerodynamical forces, moments, and power do not vary with turbulent intensity, but their fluctuations grow as turbulent intensity increases.

[Phys. Rev. Fluids 4, 013103] Published Wed Jan 16, 2019

Effect of Mach number and volume fraction in air-shock interacting with a bed of randomly distributed spherical particles

Tue, 01/15/2019 - 10:00

Author(s): Y. Mehta, K. Salari, T. L. Jackson, and S. Balachandar

Shock interaction with a bed of randomly distributed particles leads to large variation in the drag forces, highlighting the impact of neighboring particles, and indicating a need for point-particle force models that account for this drag variation.

[Phys. Rev. Fluids 4, 014303] Published Tue Jan 15, 2019

Damping of surface waves by floating particles

Tue, 01/15/2019 - 10:00

Author(s): Bruce R. Sutherland and Neil J. Balmforth

Surface waves in the presence of floating particles are shown to arrest in finite-time as a consequence of dissipation associated with flow between the particles; implications for wave damping by sea ice are discussed.

[Phys. Rev. Fluids 4, 014804] Published Tue Jan 15, 2019

Time evolution equation for advective heat transport as a constraint for optimal bounds in Rayleigh-Bénard convection

Mon, 01/14/2019 - 10:00

Author(s): A. Tilgner

Upper bounds on quantities of interest in Rayleigh-Bénard convection are derived by including a constraint derived from the time evolution equation for advective heat transport. This additional constraint leads to improved bounds on the toroidal dissipation.

[Phys. Rev. Fluids 4, 014601] Published Mon Jan 14, 2019

Influence of spanwise rotation and scalar boundary conditions on passive scalar transport in turbulent channel flow

Mon, 01/14/2019 - 10:00

Author(s): Geert Brethouwer

Direct numerical simulations of passive scalar transport in turbulent channel flow subject to spanwise rotation are performed with two different scalar boundary conditions. A key finding is that rotation strongly reduces the turbulent Prandtl number, irrespective of the scalar boundary conditions.

[Phys. Rev. Fluids 4, 014602] Published Mon Jan 14, 2019

Numerical simulations of the shear instability and subsequent degeneration of basin scale internal standing waves

Mon, 01/14/2019 - 10:00

Author(s): Andrew Grace, Marek Stastna, and Francis J. Poulin

High resolution numerical simulations of the evolution and subsequent degeneration of large amplitude internal standing waves are presented. Emphasized are examples of large amplitude wave train formation coexisting with shear instability.

[Phys. Rev. Fluids 4, 014802] Published Mon Jan 14, 2019

Internal gravity waves generated by an impulsive plume

Mon, 01/14/2019 - 10:00

Author(s): Alan Brandt and Kara R. Shipley

Laboratory experiments demonstrate the generation of internal waves by a short-duration impulsive plume. After the plume descends to a maximum depth, it rebounds to an equilibrium level where the ensuing oscillation results in the generation of a propagating internal wave field.

[Phys. Rev. Fluids 4, 014803] Published Mon Jan 14, 2019

Reduced-order modeling of fully turbulent buoyancy-driven flows using the Green's function method

Fri, 01/11/2019 - 10:00

Author(s): M. A. Khodkar, Pedram Hassanzadeh, Saleh Nabi, and Piyush Grover

A novel method for reduced-order modeling of turbulent flows is discussed in the context of fully turbulent Rayleigh-Bénard convection. The method can be used to control the turbulent mean profiles, to discern the spectral properties of turbulent flows, and to improve the data-driven techniques.

[Phys. Rev. Fluids 4, 013801] Published Fri Jan 11, 2019

Breakup of a particulate suspension jet

Thu, 01/10/2019 - 10:00

Author(s): J. Château and H. Lhuissier

A falling jet of a concentrated suspension is found to break abruptly where its diameter becomes a few particles thick. A simple model explains the jet breakup length observed experimentally.

[Phys. Rev. Fluids 4, 012001(R)] Published Thu Jan 10, 2019

Stall of airfoils with blunt noses at low to moderately high Reynolds numbers

Thu, 01/10/2019 - 10:00

Author(s): Matthew G. Kraljic and Zvi Rusak

The onset of leading-edge stall on stationary, smooth, thin, two-dimensional airfoils with blunter than classical nose shapes at low to moderately high Reynolds number flows is studied. Global stall is delayed to higher angles of attack as nose bluntness is increased.

[Phys. Rev. Fluids 4, 014101] Published Thu Jan 10, 2019

Influence of inlet flow profiles on swirling flow dynamics in a finite-length pipe

Thu, 01/10/2019 - 10:00

Author(s): Yuxin Zhang, Zvi Rusak, and Shixiao Wang

The influence of various inlet swirling flow profiles on the manifold of steady axisymmetric states of flows, their domain of attraction, and on flow dynamics in a straight, long circular pipe is investigated.

[Phys. Rev. Fluids 4, 014701] Published Thu Jan 10, 2019