New Papers in Fluid Mechanics

Experimental adventures in variable-density mixing

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Kathy Prestridge

Variable-density has important physical effects on turbulence, including driving mixing from small to large scales. Many compressible and variable-density flow applications cannot be simulated directly. Recent experimental measurements have implications for modeling and underresolved simulations.


[Phys. Rev. Fluids 3, 110501] Published Wed Nov 21, 2018

Particle-induced viscous fingering: Review and outlook

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Rui Luo, Yun Chen, and Sungyon Lee

When a mixture of noncolloidal particles and oil displaces air inside a Hele-Shaw cell, particles accumulate on the interface and cause fingering by generating an unstable viscosity gradient inside the suspension. A review and new data of the fingering onset and evolution are presented.


[Phys. Rev. Fluids 3, 110502] Published Wed Nov 21, 2018

Role of singularities in hydrodynamics

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): J. Eggers

The image of a turbulent jet reveals complex spatial patterns, which result from the decay of turbulent eddies into smaller and smaller structures. Here we lay out a road map to describe such patterns as a result of singularities which possess both a nontrivial spatial structure, and exhibit instability as they progress toward smaller and smaller scales.


[Phys. Rev. Fluids 3, 110503] Published Wed Nov 21, 2018

Bubble puzzles: From fundamentals to applications

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Detlef Lohse

This paper sketches my personal scientific bubble journey, starting with single-bubble sonoluminescence, continuing with sound emission and scattering of bubbles, cavitation, snapping shrimp, impact events, air entrainment, and surface micro- and nanobubbles, and finally arriving at effective force models for bubbles and dispersed bubbly two-phase flow.


[Phys. Rev. Fluids 3, 110504] Published Wed Nov 21, 2018

Liquid fraction profile in a liquid foam under an applied voltage

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Anne-Laure Biance and Oriane Bonhomme

Liquid transport in a dry foam, a deformable porous material, in the presence of an applied electric field, is computed in the limits of rigid and mobile interfaces. The evolution of the liquid distribution is diffusive-like and significantly affected by the hydrodynamic boundary conditions.


[Phys. Rev. Fluids 3, 110505] Published Wed Nov 21, 2018

Revealing hidden information with quadratic products of acoustic field amplitudes

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): David R. Dowling

Since the development of propagating-wave-based remote sensing more than a century ago, signal analysis has been limited to in-band recorded frequencies. However, this limitation is artificial. A new discovery from the realm of sonar shows that remote sensing is possible at out-of-band frequencies.


[Phys. Rev. Fluids 3, 110506] Published Wed Nov 21, 2018

Direct numerical simulations of premixed and stratified flame propagation in turbulent channel flow

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Andrea Gruber, Edward S. Richardson, Konduri Aditya, and Jacqueline H. Chen

Flashback is a key operational and safety issue for modern low-emission burners. With direct numerical simulations we study upstream flame movement through the turbulent flow within a channel and address the marked change in flashback behavior when the fuel and oxidant mixture is not homogeneous.


[Phys. Rev. Fluids 3, 110507] Published Wed Nov 21, 2018

Lubricated-to-frictional shear thickening scenario in dense suspensions

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Jeffrey F. Morris

A scenario in which shear thickening results from a transition of interactions between suspended particles from lubricated to frictional (LF) with increasing stress is described, with a presentation of primary results and a perspective on outstanding questions which are raised by the LF mechanism.


[Phys. Rev. Fluids 3, 110508] Published Wed Nov 21, 2018

Sensitivity analysis of thermoacoustic instability with adjoint Helmholtz solvers

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): Matthew P. Juniper

The power density in a rocket engine is 50 GW/m3. If flame oscillations lock into the acoustic modes of the chamber, the resultant noise can blow up the engine. This paper explains pedagogically, with example code, how best to use adjoint methods to passively control this thermoacoustic instability.


[Phys. Rev. Fluids 3, 110509] Published Wed Nov 21, 2018

Visualization study of thermal counterflow of superfluid helium in the proximity of the heat source by using solid deuterium hydride particles

Physical Review Fluids - Wed, 11/21/2018 - 10:00

Author(s): P. Švančara, P. Hrubcová, M. Rotter, and M. La Mantia

An experimental investigation of steady-state thermal counterflow of superfluid 4He indicates that, in the range of investigated parameters, interactions between flow-probing particles and tangles of quantized vortices are appreciably influenced not only by the tangle geometry but also by the particle inertia.


[Phys. Rev. Fluids 3, 114701] Published Wed Nov 21, 2018

Quaternion structure of azimuthal instabilities

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): Giulio Ghirardo and Mirko R. Bothien

An investigation of fluctuations occurring in rotationally symmetric systems draws a link between these fluctuations and light polarization, two-state quantum systems, and quaternion numbers. An ansatz is proposed to study this class of problems and is applied it to azimuthal acoustic instabilities in an annular combustion chamber.


[Phys. Rev. Fluids 3, 113202] Published Tue Nov 20, 2018

Taylor Couette instability in disk suspensions

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): J. J. J. Gillissen and H. J. Wilson

A theoretical study shows that adding disk-shaped particles to the fluid between counter-rotating cylinders reduces the onset-speed for secondary flow.


[Phys. Rev. Fluids 3, 113903] Published Tue Nov 20, 2018

Device design and flow scaling for liquid sheet jets

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): Byunghang Ha (하병항), Daniel P. DePonte, and Juan G. Santiago

A design for and experimental study of microfluidic nozzles that generate thin liquid sheet jets is presented. A parametric study is conducted by varying nozzle geometry, flow rate, and fluid type, and scaling theories to scale and predict jet sheet thickness, width, and length are proposed.


[Phys. Rev. Fluids 3, 114202] Published Tue Nov 20, 2018

Conditional stability of particle alignment in finite-Reynolds-number channel flow

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): Anupam Gupta, Pascale Magaud, Christine Lafforgue, and Micheline Abbas

If flow inertia is finite at the particle scale in a channel, particles align parallel to the flow streamlines, forming stable trainlike structures near the walls at low concentration. A numerical investigation finds that hydrodynamic interactions prohibit train formation at lengths exceeding the channel height.


[Phys. Rev. Fluids 3, 114302] Published Tue Nov 20, 2018

Decomposition of the Reynolds stress from filtered data

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): Markus Klein and Massimo Germano

An exact relation between the Reynolds stress and the resolved stress of filtered data is derived and tested in order to quantify the interference effect between mean and subfilter scales. Besides the well-known resolved and subfilter stresses, two additional terms appear in the decomposition.


[Phys. Rev. Fluids 3, 114606] Published Tue Nov 20, 2018

Nonlinear harmonic generation by internal waves in a density staircase

Physical Review Fluids - Tue, 11/20/2018 - 10:00

Author(s): Scott Wunsch

Climate change in the Arctic Ocean will subject its thermohaline staircases to increased internal wave activity. An exploration of the nonlinear conversion of incident waves to trapped staircase waves identifies wave number and frequency bands where energy transfer may be significant.


[Phys. Rev. Fluids 3, 114803] Published Tue Nov 20, 2018

Lagrangian acceleration in Rayleigh-Bénard convection at various aspect ratios

Physical Review Fluids - Mon, 11/19/2018 - 10:00

Author(s): Jin-Tae Kim, Shikun Shen, Steven L. DiMarco, Yaqing Jin, and Leonardo P. Chamorro

Lagrangian dynamics of turbulent Rayleigh-Bénard convection is studied experimentally with 3D particle tracking velocimetry at various aspect ratios G. Insight on the pair dispersion, conditional acceleration probability density functions, and roll dynamics induced by G was found from nearly 3.5×107 events.


[Phys. Rev. Fluids 3, 113502] Published Mon Nov 19, 2018

Front evaporation effects on wicking in two- and three-dimensional porous domains

Physical Review E - Fri, 11/16/2018 - 10:00

Author(s): Eric M. Benner and Dimiter N. Petsev

We present the equations for wicking in two- and three-dimensional porous media when liquid is evaporating through the wet front using the Green–Ampt saturated capillary flow model in polar and spherical geometries. The time-dependent behavior of two-dimensional wicking influenced by front interface...


[Phys. Rev. E 98, 053104] Published Fri Nov 16, 2018

Material transport in the left ventricle with aortic valve regurgitation

Physical Review Fluids - Fri, 11/16/2018 - 10:00

Author(s): Giuseppe Di Labbio, Jérôme Vétel, and Lyes Kadem

An investigation of a leaking aortic valve finds that it prompts double-jet filling in the compliant left ventricle of the heart, inducing complex and inefficient blood transport. This gives rise to increased blood residence time and the emergence of attracting material lines, presenting favorable conditions for thrombus formation.


[Phys. Rev. Fluids 3, 113101] Published Fri Nov 16, 2018

Characterization of superimposed instabilities in the planar extensional flow of viscoelastic fluids

Physical Review Fluids - Fri, 11/16/2018 - 10:00

Author(s): F. A. Cruz and M. A. Alves

Cross-slot devices are routinely used to study the extension of high molecular weight polymer molecules and DNA in solution. We simulate the extensional flow of Boger fluids in an optimised cross-slot rheometer and investigate various emerging time-dependent instabilities.


[Phys. Rev. Fluids 3, 113301] Published Fri Nov 16, 2018

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