Physical Review Fluids

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

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

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

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

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

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

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

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

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

Material transport in the left ventricle with aortic valve regurgitation

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

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

Inertial range skewness of the longitudinal velocity derivative in locally isotropic turbulence

Fri, 11/16/2018 - 10:00

Author(s): S. Sukoriansky, E. Kit, E. Zemach, S. Midya, and H. J. S. Fernando

A velocity derivative skewness akin to inertial-scale motions of turbulence is introduced and studied analytically, numerically, and experimentally. As an alternative to a conventional fine-scale parameter, it has an advantage in measurability while retaining a connection to vorticity dynamics.

[Phys. Rev. Fluids 3, 114605] Published Fri Nov 16, 2018

Probing turbulent superstructures in Rayleigh-Bénard convection by Lagrangian trajectory clusters

Thu, 11/15/2018 - 10:00

Author(s): Christiane Schneide, Ambrish Pandey, Kathrin Padberg-Gehle, and Jörg Schumacher

Large-scale patterns in three-dimensional turbulent Rayleigh-Bénard convection in a large-aspect-ratio cell are probed by the clustering of Lagrangian particle trajectories.

[Phys. Rev. Fluids 3, 113501] Published Thu Nov 15, 2018

Particle-laden exchange flows in inclined pipes

Thu, 11/15/2018 - 10:00

Author(s): Nima Mirzaeian and Kamran Alba

Intrusion of a particle-laden mixture into a pure fluid is studied experimentally within a duct. Applications are found in the discharge of slurries, mine tailings, pastes, sludge, effluents, and sewage. Exotic sedimentary, transitionary, and mixing regimes are found over various inclination angles.

[Phys. Rev. Fluids 3, 114301] Published Thu Nov 15, 2018

Coexistence of solitons and extreme events in deep water surface waves

Tue, 11/13/2018 - 10:00

Author(s): A. Cazaubiel, G. Michel, S. Lepot, B. Semin, S. Aumaître, M. Berhanu, F. Bonnefoy, and E. Falcon

An experimental study reveals a new statistical regime for 1D propagation of deep-water gravity waves where coherent structures (solitons, extreme events) coexist with random waves. Such a state is predicted theoretically by integrable turbulence but thus far had not been observed in this context.

[Phys. Rev. Fluids 3, 114802] Published Tue Nov 13, 2018

Stability of the Blasius boundary layer over a heated plate in a temperature-dependent viscosity flow

Fri, 11/09/2018 - 10:00

Author(s): R. Miller, S. J. Garrett, P. T. Griffiths, and Z. Hussain

A stability analysis of the Blasius boundary layer formed by a fluid with a temperature-dependent viscosity is examined. The results inform whether hydrodynamically unstable flows may exist inside chemical vapor deposition reactors (CVD) and how a comprehensive CVD stability model can be developed.

[Phys. Rev. Fluids 3, 113902] Published Fri Nov 09, 2018

Experimental investigations of liquid falling films flowing under an inclined planar substrate

Fri, 11/09/2018 - 10:00

Author(s): Alexandros Charogiannis, Fabian Denner, Berend G. M. van Wachem, Serafim Kalliadasis, Benoit Scheid, and Christos N. Markides

Space/time-resolved film-thickness data are presented for liquid films flowing under an inverted planar substrate. Different flow regimes are observed depending on the inclination, liquid properties, and Reynolds number, with waves characterized by pronounced three-dimensionality and rivulet formation.

[Phys. Rev. Fluids 3, 114002] Published Fri Nov 09, 2018

Topographical effects of roughness on turbulence statistics in roughness sublayer

Fri, 11/09/2018 - 10:00

Author(s): J. Yuan and M. Aghaei Jouybari

Current understanding of turbulence in the vicinity of surface roughness is mostly limited to narrow-scale or regular roughness geometries. A numerical analysis shows how various scales of a multiscale, realistic roughness affect friction, momentum balance, and turbulence production in the roughness sublayer.

[Phys. Rev. Fluids 3, 114603] Published Fri Nov 09, 2018

Structure, dynamics, and reconnection of vortices in a nonlocal model of superfluids

Thu, 11/08/2018 - 10:00

Author(s): Jason Reneuve, Julien Salort, and Laurent Chevillard

A nonlocal version of the Gross-Pitaevskii equation is investigated. The role of rotons in vortex reconnection is probed through numerical simulations of both local (standard) and nonlocal models. Observed dynamics are compared with the predictions of the local induction approximation.

[Phys. Rev. Fluids 3, 114602] Published Thu Nov 08, 2018

Characteristics of turbulent boundary layer large scale motions using direct fluctuating wall shear stress measurements

Thu, 11/08/2018 - 10:00

Author(s): Rommel J. Pabon, Lawrence Ukeiley, Mark Sheplak, and Casey Barnard Keane

A microelectromechanical-systems-based floating element wall-shear-stress sensor (1×1 mm) is validated in a turbulent boundary layer for its ability to measure characteristics of large-scale motions.

[Phys. Rev. Fluids 3, 114604] Published Thu Nov 08, 2018

Control of flow around a low Reynolds number airfoil using longitudinal strips

Wed, 11/07/2018 - 10:00

Author(s): Seunghyun Cho, Jooha Kim, and Haecheon Choi

Longitudinal strips are suggested as a new device that can significantly increase the aerodynamic performance of a low Reynolds number airfoil at post-stall angles of attack. Its mechanism relies on the generation of corner vortices that delay flow separation on the airfoil suction surface.

[Phys. Rev. Fluids 3, 113901] Published Wed Nov 07, 2018