On nonhydrostatic coastal model simulations of shear instabilities in a stratified shear flow at high Reynolds number

Rotating flow in which the angular velocity decreases outward while the angular momentum increases is known as ‘quasi-Keplerian’. Despite the general tendency of shear flow to break down into turbulence, this type of flow seems to maintain stability at very large Reynolds number, even when nonlinearly perturbed, a behaviour that strongly influences our understanding of astrophysical accretion discs. Investigating these flows in the laboratory is difficult because secondary Ekman flows, caused by the retaining Couette cylinders, can become turbulent on their own. A recent high Reynolds number numerical study by Lopez & Avila (J. Fluid Mech., vol. 817, 2017, pp. 21–34) reconciles apparently discrepant laboratory experiments by confirming that this secondary flow recedes toward the axial boundaries of the container as the Reynolds number is increased, a result that enhances our understanding of nonlinear quasi-Keplerian flow stability.

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Dislodging a sessile drop by a high-Reynolds-number shear flow at subfreezing temperatures

Physical Review E ◽

10.1103/physreve.92.023007 ◽

2015 ◽

Vol 92 (2) ◽

Cited By ~ 16

Author(s):

Ilia V. Roisman ◽

Antonio Criscione ◽

Cameron Tropea ◽

Deepak Kumar Mandal ◽

Alidad Amirfazli

Keyword(s):

Reynolds Number ◽

Shear Flow ◽

High Reynolds Number ◽

Sessile Drop ◽

High Reynolds

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Dissipation-range geometry and scalar spectra in sheared stratified turbulence

Journal of Fluid Mechanics ◽

10.1017/s0022112099006734 ◽

1999 ◽

Vol 401 ◽

pp. 209-242 ◽

Cited By ~ 53

Author(s):

WILLIAM D. SMYTH

Keyword(s):

Reynolds Number ◽

Shear Flow ◽

Turbulent Flows ◽

Passive Scalar ◽

Stratified Turbulence ◽

Stratified Shear Flow ◽

Dependent Strain ◽

Parallel Shear Flow ◽

High Reynolds ◽

Dissipation Range

Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stratified shear flow are used to examine the geometry of the dissipation range in a variety of flow regimes. As the buoyancy and shear Reynolds numbers that quantify the degree of isotropy in the dissipation range increase, alignment statistics evolve from those characteristic of parallel shear flow to those found previously in studies of stationary, isotropic, homogeneous turbulence (e.g. Ashurst et al. 1987; She et al. 1991; Tsinober et al. 1992). The analysis yields a limiting value for the mean compression rate of scalar gradients that is expected to be characteristic of all turbulent flows at sufficiently high Reynolds number.My main focus is the value of the constant q that appears in both the Batchelor (1959) and Kraichnan (1968) theoretical forms for the passive scalar spectrum. Taking account of the effects of time-dependent strain, I propose a revised estimate of q, denoted qe, which appears to agree with spectral shapes derived from simulations and observations better than do previous theoretical estimates. The revised estimate is qe = 7.3±4, and is expected to be valid whenever the buoyancy Reynolds number exceeds O(102). The Kraichnan (1968) spectral form, in which effects of intermittency are accounted for, provides a better fit to the DNS results than does the Batchelor (1959) form.

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