Physical Review Fluids

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Electrophoretic slip-tuned particle migration in microchannel viscoelastic fluid flows

Thu, 07/05/2018 - 11:00

Author(s): Di Li and Xiangchun Xuan

Particles migrate towards the center or walls of a rectangular microchannel if they lead or lag a viscoelastic fluid flow due to positive and negative electrophoresis, respectively. This is opposite to a Newtonian fluid. We attribute this to the shear-induced extra lift in a viscoelastic fluid.

[Phys. Rev. Fluids 3, 074202] Published Thu Jul 05, 2018

Dynamics of growth and detachment of an isolated bubble on an inclined surface

Tue, 07/03/2018 - 11:00

Author(s): M. Lebon, J. Sebilleau, and C. Colin

Experiments on air bubbles nucleated on an inclined plate show the importance of the bubble foot shape. A new expression for the capillary force is proposed to predict the bubble detachment diameter.

[Phys. Rev. Fluids 3, 073602] Published Tue Jul 03, 2018

Rheological response of nonspherical granular flows down an incline

Tue, 07/03/2018 - 11:00

Author(s): R. C. Hidalgo, B. Szabó, K. Gillemot, T. Börzsönyi, and T. Weinhart

Our discrete element simulations and laboratory experiments revealed that density and friction are well-defined functions of the effective inertial number, which fully captures the effect of grain elongation.

[Phys. Rev. Fluids 3, 074301] Published Tue Jul 03, 2018

Splash of a drop impacting onto a solid substrate wetted by a thin film of another liquid

Mon, 07/02/2018 - 11:00

Author(s): Hannah M. Kittel, Ilia V. Roisman, and Cameron Tropea

Experiments on single drop impacts on thin films of another liquid are analyzed theoretically over 8 orders of magnitude in viscosity ratio νf/νd. Away from νf≊νd we find that the K-numbers determine the splashing threshold and in that region a modified K-number, which we introduce, is needed.

[Phys. Rev. Fluids 3, 073601] Published Mon Jul 02, 2018

Hydrodynamic stress correlations in fluid films driven by stochastic surface forcing

Fri, 06/29/2018 - 11:00

Author(s): Masoud Mohammadi-Arzanagh, Saeed Mahdisoltani, Rudolf Podgornik, and Ali Naji

Driving a planar thin film of a compressible viscous fluid using random surface forcing leads to remarkable fluctuation-induced stresses on the bounding surfaces of the film, exhibiting power-law, or even non-decaying, behaviors as a function of the film thickness.

[Phys. Rev. Fluids 3, 064201] Published Fri Jun 29, 2018

Identifying Faraday rogue wave precursors from surrounding waveform information

Thu, 06/28/2018 - 11:00

Author(s): Hsiang-Ying Chen, Chun-Yu Liu, and Lin I

Experiments find that rogue wave events for Faraday waves tend to be preceded one period before by a surrounding waveform of high angular average and small variation of wave height.

[Phys. Rev. Fluids 3, 064401] Published Thu Jun 28, 2018

Preferential concentration of noninertial buoyant particles in the ocean mixed layer under free convection

Thu, 06/28/2018 - 11:00

Author(s): Tomás Chor, Di Yang, Charles Meneveau, and Marcelo Chamecki

A large eddy simulation is used to study the surface patterns of noninertial passive buoyant particles in the ocean mixed layer. A mechanism for preferential concentration that is independent of inertial effects is then identified and quantified as a function of the terminal rise velocity.

[Phys. Rev. Fluids 3, 064501] Published Thu Jun 28, 2018

Slip boundary conditions for the compressible Navier-Stokes equations for a polyatomic gas

Wed, 06/27/2018 - 11:00

Author(s): Masanari Hattori, Shingo Kosuge, and Kazuo Aoki

The slip boundary conditions for the compressible Navier-Stokes equations for a polyatomic gas are derived from kinetic theory using the ellipsoidal statistical model of the Boltzmann equation. The slip coefficients for some typical polyatomic gases are presented explicitly.

[Phys. Rev. Fluids 3, 063401] Published Wed Jun 27, 2018

Effects of particle size and density on dust dispersion behind a moving shock

Tue, 06/26/2018 - 11:00

Author(s): Shuyue Lai, Ryan W. Houim, and Elaine S. Oran

A continuum granular model is used to investigate dust dispersion and segregation behind a moving shock in a polydispersed system. The results indicate that larger and heavier particles are more dispersed than smaller and lighter ones. The reasons are discussed in terms of the governing forces.

[Phys. Rev. Fluids 3, 064306] Published Tue Jun 26, 2018

Intrinsic viscosity of a suspension of weakly Brownian ellipsoids in shear

Tue, 06/26/2018 - 11:00

Author(s): G. Almondo, J. Einarsson, J. R. Angilella, and B. Mehlig

We calculate, by numerical simulation of a Langevin equation, how the intrinsic viscosity of a dilute suspension of small (triaxial) ellipsoids depends on the degree to which triaxiality is broken. We find that the intrinsic viscosity decreases as the shape becomes less axisymmetric.

[Phys. Rev. Fluids 3, 064307] Published Tue Jun 26, 2018

Turbulence and turbulent pattern formation in a minimal model for active fluids

Mon, 06/25/2018 - 11:00

Author(s): Martin James, Wouter J. T. Bos, and Michael Wilczek

A minimal continuum model for active fluids exhibits turbulence as well as a dynamic hexagonal vortex lattice state, which is preceded by an extended turbulent transient.

[Phys. Rev. Fluids 3, 061101(R)] Published Mon Jun 25, 2018

Instabilities of MHD flows driven by traveling magnetic fields

Mon, 06/25/2018 - 11:00

Author(s): K. Sandeep Reddy, Stephan Fauve, and Christophe Gissinger

A numerical study shows that an electrically conducting fluid driven by a traveling magnetic field always exhibits a Joule dissipation larger than the viscous one. This surprising result suggests the existence of an upper bound for the efficiency of electromagnetic pumps, which can’t exceed 50%.

[Phys. Rev. Fluids 3, 063703] Published Mon Jun 25, 2018

Exploration of thermal counterflow in He II using particle tracking velocimetry

Fri, 06/22/2018 - 11:00

Author(s): Brian Mastracci and Wei Guo

Particle tracking velocimetry is applied to thermal counterflow in superfluid helium (He II), and the first method for separately analyzing the normal fluid and quantized vortex tangle velocities is presented, opening the door to new quantitative measurements of quantum turbulence.

[Phys. Rev. Fluids 3, 063304] Published Fri Jun 22, 2018

Orientation dynamics of dilute functionalized graphene suspensions in oscillatory flow

Wed, 06/20/2018 - 11:00

Author(s): Giovanniantonio Natale, Naveen K. Reddy, Robert K. Prud'homme, and Jan Vermant

Orientation dynamics of graphene suspensions is investigated in oscillatory shear flow via flow dichroism. To evaluate whether graphene sheets behave as flexible or rigid sheets during flow, the experimental data are compared with predictions from a single particle Smoluchowski equation for spheroids.

[Phys. Rev. Fluids 3, 063303] Published Wed Jun 20, 2018

Stability of melt flow during magnetic sonication in a floating zone configuration

Tue, 06/19/2018 - 11:00

Author(s): I. Grants and G. Gerbeth

Combined static and alternating magnetic fields are shown to create an oscillating pressure that can cause cavitation in molten metals. A time-averaged flow is also excited, consisting of two tori squeezed to thin boundary layers. Flow instability develops as a standing wave between these tori.

[Phys. Rev. Fluids 3, 063902] Published Tue Jun 19, 2018

Microtransformers: Controlled microscale navigation with flexible robots

Mon, 06/18/2018 - 11:00

Author(s): Thomas D. Montenegro-Johnson

Janus-like rods which can be externally switched between straight, U, and S shapes give the possibility of steering individual rods within a group through a complex geometry.

[Phys. Rev. Fluids 3, 062201(R)] Published Mon Jun 18, 2018

Role of hydrodynamic shear layer stability in driving combustion instability in a premixed propane-air backward-facing step combustor

Mon, 06/18/2018 - 11:00

Author(s): Santosh Hemchandra, Santosh Shanbhogue, Seunghyuck Hong, and Ahmed F. Ghoniem

With numerical methods and analysis of existing experimental results we show that combustion instability in a backward-facing step combustor can be maintained either with weak coupling between acoustic and hydrodynamic modes (semi-open loop) or with strong coupling (fully closed loop).

[Phys. Rev. Fluids 3, 063201] Published Mon Jun 18, 2018

Effects of finite spatial and temporal resolution in direct numerical simulations of incompressible isotropic turbulence

Mon, 06/18/2018 - 11:00

Author(s): P. K. Yeung, K. R. Sreenivasan, and S. B. Pope

A study combining spectral filtering and numerical simulations at enhanced spatial and/or temporal resolution is used to clarify the proper scaling of dissipation and enstrophy in forced incompressible isotropic turbulence.

[Phys. Rev. Fluids 3, 064603] Published Mon Jun 18, 2018

Wall slip of complex fluids: Interfacial friction versus slip length

Fri, 06/15/2018 - 11:00

Author(s): Benjamin Cross, Chloé Barraud, Cyril Picard, Liliane Léger, Frédéric Restagno, and Élisabeth Charlaix

Experiments with a complex fluid in an oscillating atomic force microscope find that the wall slip is well characterised by a real Navier interfacial friction coefficient instead of the usual slip height.

[Phys. Rev. Fluids 3, 062001(R)] Published Fri Jun 15, 2018

From hindered to promoted settling in dispersions of attractive colloids: Simulation, modeling, and application to macromolecular characterization

Fri, 06/15/2018 - 11:00

Author(s): Andrew M. Fiore, Gang Wang, and James W. Swan

Immersed boundary simulations are used to study settling in dispersions of sticky colloids and to develop an empirical model for the settling rate that is in good agreement with experiments. The model is applied to characterize attractive interactions in concentrated macromolecular solutions.

[Phys. Rev. Fluids 3, 063302] Published Fri Jun 15, 2018