Numerical validation of scaling laws for stratified turbulence

Abstract

Recent theoretical progress using multiscale asymptotic analysis has revealed various possible regimes of stratified turbulence. Notably, buoyancy transport can either be dominated by advection or diffusion, depending on the effective Péclet number of the flow. Two types of asymptotic models have been proposed, which yield measurably different predictions for the characteristic vertical velocity and length scale of the turbulent eddies in both diffusive and non-diffusive regimes. The first, termed a `single-scale model', is designed to describe flow structures having large horizontal and small vertical scales, while the second, termed a `multiscale model', additionally incorporates flow features with small horizontal scales, and reduces to the single-scale model in their absence. By comparing predicted vertical velocity scaling laws with direct numerical simulation data, we show that the multiscale model correctly captures the properties of strongly stratified turbulence within regions dominated by small-scale isotropic motions, whose volume fraction decreases as the stratification increases. Meanwhile its single-scale reduction accurately describes the more orderly, layer-like, quiescent flow outside those regions.

arXiv commentResubmitted to JFM Rapids after referee review

References in corpus (5)

• Dynamics of fingering convection I: Small-scale fluxes and large-scale instabilities
• The dynamics of stratified horizontal shear flows at low Péclet number
• Horizontal shear instabilities at low Prandtl number
• Exploiting self-organized criticality in strongly stratified turbulence
• Critical Balance and Scaling of Strongly Stratified Turbulence at Low Prandtl Number

Cited by in corpus (2)

• Spontaneous generation of helical flows by salt fingers
• Centrifugal instability of Taylor-Couette flow in stratified and diffusive fluids