Kelvin Helmholtz Instability “Tube” and “Knot” Dynamics, Part III: Extension of Elevated Turbulence and Energy Dissipation into Increasingly Viscous Flows

Abstract

A companion paper by Fritts et al. (2023) reviews extensive evidence for Kelvin-Helmholtz instability (KHI) “tube” and “knot” (T&K) dynamics at multiple altitudes in the atmosphere and in the oceans that reveal these dynamics to be widespread. A second companion paper by Fritts and Wang (2023) reveals KHI T&K events at larger and smaller scales to arise on multiple highly-stratified sheets in a direct numerical simulation (DNS) of idealized, multi-scale gravity wave – fine structure interactions. These studies reveal the diverse environments in which KHI T&K dynamics arise and suggest their potentially ubiquitous occurrence throughout the atmosphere and oceans. This paper describes DNS of multiple KHI evolutions in wide and narrow domains enabling and excluding T&K dynamics. These DNS employ common initial conditions, but are performed for decreasing Reynolds numbers, Re, to explore whether T&K dynamics enable enhanced KHI-induced turbulence where it would be weaker or not otherwise occur. The major results are that KHI T&K dynamics extend elevated turbulence intensities and energy dissipation rates, ε, to smaller Re. We expect these results to have important implications for improving parameterizations of KHI-induced turbulence in the atmosphere and oceans.