Asymptotic dynamics of high dynamic range stratified turbulence

作     者：Portwood, G.D. de Bruyn Kops, S.M. Caulfield, C.P. 

作者机构：Department of Mechanical and Industrial Engineering University of Massachusetts Amherst01003 United States  Computational Physics Division Los Alamos National Laboratory Los Alamos87545 United States BP Institute University of Cambridge CambridgeCB3 0EZ United Kingdom Department of Applied Mathematics & Theoretical Physics University of Cambridge CambridgeCB3 0WA United Kingdom 

出 版 物：《arXiv》 (arXiv)

年 卷 期：2019年

核心收录：

主　　题：Kinetic energy 

摘      要：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, LO = pǫ/N3, and the Kolmogorov length scale, LK = (ν3/ǫ)1/4, up to Reb ≡ (LO/LK)4/3 = ǫ/(νN2) ∼ O(1000), where ǫ 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 Reb 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 Reb increases above 100, there is a slight decrease in the turbulent flux coefficient Γ = χ/ǫ, where χ is the dissipation rate of buoyancy variance, but, for this flow, there is no evidence of the commonly suggested Γ ∝ Reb−1/2 dependence when 100 ≤ Reb ≤ 1000. Copyright © 2019, The Authors. All rights reserved.