Physical Review Fluids

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Updated: 14 hours 54 min ago

Global linear instability of rotating-cone boundary layers in a quiescent medium

Mon, 04/08/2019 - 11:00

Author(s): Christian Thomas and Christopher Davies

Numerical simulations of disturbance development in the family of rotating-cone boundary layers illustrates that for sufficiently large azimuthal mode numbers, a form of global linear instability ensues that is characterized by a faster than exponential temporal growth.

[Phys. Rev. Fluids 4, 043902] Published Mon Apr 08, 2019

Hydrodynamic interactions in polar liquid crystals on evolving surfaces

Mon, 04/08/2019 - 11:00

Author(s): Ingo Nitschke, Sebastian Reuther, and Axel Voigt

The flow of passive and active polar liquid crystals on evolving surfaces is considered. The models are derived as a thin-film limit, and a finite element method is used to study the effect of hydrodynamics on the interplay of topology, geometric properties, and defect dynamics.

[Phys. Rev. Fluids 4, 044002] Published Mon Apr 08, 2019

Transition to chaos in an acoustically driven cavity flow

Mon, 04/08/2019 - 11:00

Author(s): Gaby Launay, Tristan Cambonie, Daniel Henry, Alban Pothérat, and Valéry Botton

We show that a cavity flow driven by acoustic streaming can sustain low-dimensional chaos. Frequency and nonlinear times series analyses reveal a novel path to chaos with a sequence of two-way transitions between nonchaotic and chaotic states with steps where the dynamics drastically simplifies.

[Phys. Rev. Fluids 4, 044401] Published Mon Apr 08, 2019

Velocity fluctuations in a dilute suspension of viscous vortex rings

Mon, 04/08/2019 - 11:00

Author(s): Thomas A. Morrell, Saverio E. Spagnolie, and Jean-Luc Thiffeault

Velocity fluctuations in a fluid due to a dilute suspension of vortex rings, such as those generated by a population of small jellyfish, are explored. The slow diffusion of momentum leads to a different stable distribution than is found for velocity fluctuations caused by microswimmers.

[Phys. Rev. Fluids 4, 044501] Published Mon Apr 08, 2019

Direct numerical simulation of a supersonic turbulent boundary layer subjected to a concave surface

Mon, 04/08/2019 - 11:00

Author(s): Xiaoshuai Wu, Jianhan Liang, and Yuxin Zhao

An investigation finds that a supersonic turbulent boundary layer is highly destabilized by a longitudinal concave surface. The intensification of vortical structures reflects the effect of turbulence amplification. Streaky turbulent motions suggest enhanced inner-outer interactions.

[Phys. Rev. Fluids 4, 044602] Published Mon Apr 08, 2019

Mathematical framework for analysis of internal energy dynamics and spectral distribution in compressible turbulent flows

Fri, 04/05/2019 - 11:00

Author(s): Ankita Mittal and Sharath S. Girimaji

A new variable φ ∼ √p is introduced to examine the dynamics of the internal energy, its mean and fluctuations, and then represent the exchange between kinetic and internal energy.

[Phys. Rev. Fluids 4, 042601(R)] Published Fri Apr 05, 2019

Fluctuating hydrodynamics of electrolytes at electroneutral scales

Fri, 04/05/2019 - 11:00

Author(s): Aleksandar Donev, Andrew J. Nonaka, Changho Kim, Alejandro L. Garcia, and John B. Bell

Electrolytes are effectively electroneutral at mesoscopic scales and the stochastic Poisson-Nernst-Planck equations are too stiff to solve numerically. We formulate theory and algorithms for the fluctuating hydrodynamics equations of charged, reactive mixtures with an electroneutral constraint.

[Phys. Rev. Fluids 4, 043701] Published Fri Apr 05, 2019

Hydrodynamically bound states of a pair of microrollers: A dynamical system insight

Fri, 04/05/2019 - 11:00

Author(s): Blaise Delmotte

Particles rotating above a floor, called microrollers, can pair together in a stable fashion. The physical conditions for such self-assembly are identified and provide a stepping stone towards understanding the formation of large motile clusters in microroller suspensions.

[Phys. Rev. Fluids 4, 044302] Published Fri Apr 05, 2019

Stochastic modeling of fluid acceleration on residual scales and dynamics of suspended inertial particles in turbulence

Thu, 04/04/2019 - 11:00

Author(s): Vladimir Sabelnikov, Alexis Barge, and Mikhael Gorokhovski

In the underresolved particle laden turbulence, we assess the intermittency effects in the carrier fluid. The stochastic subgrid acceleration model accounts for the orientation of vortical structures and for the local Reynolds number. Our statistics are in agreement with DNS and experiments.

[Phys. Rev. Fluids 4, 044301] Published Thu Apr 04, 2019

Scale-dependent anisotropy in forced stratified turbulence

Wed, 04/03/2019 - 11:00

Author(s): C. J. Lang and Michael L. Waite

Anisotropy of stratified turbulence at different length scales is investigated with direct numerical simulation. Large scales, which are dominated by pancake vortices, are the most anisotropic, while the Ozmidov and dissipation scales are increasingly isotropic at larger buoyancy Reynolds number.

[Phys. Rev. Fluids 4, 044801] Published Wed Apr 03, 2019

Inertial flow past a finite-length axisymmetric cylinder of aspect ratio 3: Effect of the yaw angle

Wed, 04/03/2019 - 11:00

Author(s): Jean-Lou Pierson, Franck Auguste, Abdelkader Hammouti, and Anthony Wachs

The flow past a finite-length yawed three-dimensional cylinder is investigated using direct numerical simulations. Various wake patterns are identified including the shedding of single-sided hairpin-shaped vortices.

[Phys. Rev. Fluids 4, 044802] Published Wed Apr 03, 2019

Spontaneous oscillations, beating patterns, and hydrodynamics of active microfilaments

Tue, 04/02/2019 - 11:00

Author(s): Brato Chakrabarti and David Saintillan

We develop a geometrically nonlinear model of the flagellar axoneme that accounts for the stochastic kinetics of molecular motors and results in spontaneous oscillations. We capture the beating patterns of sperm, cilia and Chlamydomonas and analyze their hydrodynamics through reduced order models.

[Phys. Rev. Fluids 4, 043102] Published Tue Apr 02, 2019

Pressure and spanwise velocity fluctuations in turbulent channel flows: Logarithmic behavior of moments and coherent structures

Tue, 04/02/2019 - 11:00

Author(s): Ali Mehrez, Jimmy Philip, Yoshinobu Yamamoto, and Yoshiyuki Tsuji

The logarithmic behavior of moments of the pressure and spanwise velocity fluctuations in turbulent channels is studied. Configurations of geometrically self-similar hairpin eddies play a key role in such behavior.

[Phys. Rev. Fluids 4, 044601] Published Tue Apr 02, 2019

Transport and dispersion of active particles in periodic porous media

Mon, 04/01/2019 - 11:00

Author(s): Roberto Alonso-Matilla, Brato Chakrabarti, and David Saintillan

The long-time transport of active Brownian particles flowing through a porous lattice is studied using generalized Taylor dispersion theory and Langevin simulations. The effects of motility, lattice geometry, and fluid flow on the asymptotic spreading of a dilute cloud of microswimmers are unraveled.

[Phys. Rev. Fluids 4, 043101] Published Mon Apr 01, 2019

Magnetohydrodynamic effects in a shock-accelerated gas cylinder

Mon, 04/01/2019 - 11:00

Author(s): Wolfgang J. Black, Roy C. Allen, W. Curtis Maxon, Nicholas Denissen, and Jacob A. McFarland

We numerically study the effect of magnetic field orientation and strength on a shock-accelerated gas cylinder susceptible to the Richtmyer-Meshkov instability. We find regimes where fluid mixing increases with field strength and a preferential field orientation for damping the instability.

[Phys. Rev. Fluids 4, 043901] Published Mon Apr 01, 2019

Sphere entry through an oil lens floating on water

Mon, 04/01/2019 - 11:00

Author(s): Linda B. Smolka and Clare K. McLaughlin

Entry of a sphere impacting an oil lens floating on a water surface is studied. An air-entraining cavity forms, lined by oil, which at collapse forms an oil filament connecting the upper and lower cavities. These dynamics are different than that of a sphere impacting water where no cavity forms at all.

[Phys. Rev. Fluids 4, 044001] Published Mon Apr 01, 2019

Impact of fundamental molecular kinetics on macroscopic properties of high-enthalpy flows: The case of hypersonic atmospheric entry

Fri, 03/29/2019 - 10:00

Author(s): G. Colonna, F. Bonelli, and G. Pascazio

A state-to-state approach and GPU processors are used to find the nonequilibrium vibrational distributions of O2 and N2 in a hypersonic flow past a sphere.

[Phys. Rev. Fluids 4, 033404] Published Fri Mar 29, 2019

Nonequilibrium air flow predictions with a high-fidelity direct simulation Monte Carlo approach

Fri, 03/29/2019 - 10:00

Author(s): Sergey F. Gimelshein and Ingrid J. Wysong

A conventional and high-fidelity direct simulation Monte Carlo approach is applied to a number of hypersonic cases where validation data is available. Changes in the collision model are found to have a small effect on surface properties, with nitrogen recombination being the only notable exception.

[Phys. Rev. Fluids 4, 033405] Published Fri Mar 29, 2019

Disorder characterization of porous media and its effect on fluid displacement

Fri, 03/29/2019 - 10:00

Author(s): Zhongzheng Wang, Kapil Chauhan, Jean-Michel Pereira, and Yixiang Gan

Depending on topology of pore space, different patterns of multiphase flow in porous media are observed. By analyzing pore-scale mechanisms, a phase diagram is constructed showing that wettability and structural disorder collectively affect displacement efficiency and fluid-fluid interfacial area.

[Phys. Rev. Fluids 4, 034305] Published Fri Mar 29, 2019

Investigation of inner-outer interactions in a turbulent boundary layer using high-speed particle image velocimetry

Fri, 03/29/2019 - 10:00

Author(s): Gokul Pathikonda and Kenneth T. Christensen

High-resolution, high-frame-rate particle image velocimetry measurements in a refractive index-matched flow facility are used to explore the spatiotemporal signature of outer, large-scale motions influencing near-wall, smaller scales (so-called inner-outer interactions) in a turbulent boundary layer.

[Phys. Rev. Fluids 4, 034607] Published Fri Mar 29, 2019