Turbulence energetics in stably stratified geophysical flows: Strong and weak mixing regimes
By Sergej Zilitinkevich, T. Elperin, N. Kleeorin, I. Rogachevskii, Igor Esau, T. Mauritsen, M. Miles. 2008
194 citations recorded by the source corpus.
Traditionally, turbulence energetics is characterised by turbulent kinetic energy (TKE) and modelled using solely the TKE budget equation. In stable stratification, TKE is generated by the velocity shear and expended through viscous dissipation and work against buoyancy forces. The effect of stratification is characterised by the ratio of the buoyancy gradient to squared shear, called the Richardson number, Ri. It is widely believed that at Ri exceeding a critical value, Ric, local shear cannot maintain turbulence, and the flow becomes laminar. We revise this concept by extending the energy analysis to turbulent potential and total energies (TPE, and TTE = TKE + TPE), consider their budget equations, and conclude that TTE is a conservative parameter maintained by shear in any stratification. Hence there is no ‘energetics Ric’, in contrast to the hydrodynamic‐instability threshold, Ric−instability, whose typical values vary from 0.25 to 1. We demonstrate that this interval, 0.25 < Ri < 1, separates two different turbulent regimes: strong mixing and weak mixing rather than the turbulent and the laminar regimes, as the classical concept states. This explains persistent occurrence of turbulence in the free atmosphere and deep ocean at Ri ≫ 1, clarifies the principal difference between turbulent boundary layers and free flows, and provides the basis for improving operational turbulence closure models. Copyright © 2008 Royal Meteorological Society
Subfields: Computational Mechanics, Earth-Surface Processes, Oceanography
View Paper: https://www.semanticscholar.org/paper/8a62c5cb8e26b543e4208341f2e7982fd5ae96dd
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Citations in the corpus
- A Hierarchy of Energy- and Flux-Budget (EFB) Turbulence Closure Models for Stably-Stratified Geophysical Flows (2011, methodology): “All these time scales are taken proportional to the master time scale tT. 2.2 EFB Model Equations From this point onwards we limit our analysis to the geophysical approximation and basically follow Zilitinkevich et al. (2007, 2008, 2009).”
- The Minimum Wind Speed for Sustainable Turbulence in the Nocturnal Boundary Layer (2012, background): “Recently, this picture was refined by Zilitinkevich et al. (2008), who use the concept of total turbulent energy to show that the critical Rf separates strongly turbulent states from weakly turbulent states rather than from truly laminar states.”