Title: Asymptotic Dynamics of High Dynamic Range Stratified Turbulence

Abstract

Direct numerical simulations of homogeneous sheared and stably stratified turbulence are considered to probe the asymptotic high-dynamic range regime suggested by Gargett et al. [1] and Shih et al. [2]. We consider statistically stationary configurations of the flow that span three decades in dynamic range defined by the separation between the Ozmidov length scale, L _O = √ ε/N ³, and the Kolmogorov length scale, L _K = (ν ³/ε) ^1/4 , up to Re _b ≡ (L _O/L _K) ^4/3 = ε/(νN ² ) ~ O(1000), where ε is the mean turbulent kinetic energy dissipation rate, ν is the kinematic viscosity, and N is the buoyancy frequency. We isolate the effects of Reb, particularly on irreversible mixing, from the effects of other flow parameters of stratified and sheared turbulence [3]. Specifically, we evaluate the influence of dynamic range independent of initial conditions. We present evidence that the flow approaches an asymptotic state for Re _b ⪆ 300, characterized both by an asymptotic partitioning between the potential and kinetic energies and by the approach of components of the dissipation rate to their expected values under the assumption of isotropy. As Re _b increases above 100, there is a slight decreasemore » in the turbulent flux coefficient Γ = χ/ε, where χ is the dissipation rate of buoyancy variance, but, for this flow, there is no evidence of the commonly suggested Γ ∝ Re _b ^-1/2 dependence when 100 ≤ Re _b ≤ 1000.« less

Authors:

Portwood, Gavin Dunn  ^[1];

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de Bruyn Kops, S. M. ^[2]; Caulfield, C. P. ^[3]

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+ Show Author Affiliations

1. Univ. of Massachusetts, Amherst, MA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Univ. of Massachusetts, Amherst, MA (United States)
3. Univ. of Cambridge (United Kingdom)

Publication Date:

2019-05-17

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

Domestic Funding

OSTI Identifier:

1526964

Report Number(s):

LA-UR-19-23048
Journal ID: ISSN 0031-9007; PRLTAO

Grant/Contract Number:  

89233218CNA000001

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Physical Review Letters

Additional Journal Information:

Journal Volume: 122; Journal Issue: 19; Journal ID: ISSN 0031-9007

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS