The Renormalized Perturbation Technique of successive small scales elimination is applied to turbulent flows with stable stratification. This procedure results in derivation of scale-dependent anisotropic viscosities and diffusivities that naturally incorporate the combined effect of turbulence and internal waves. In addition, this procedure ren- ders means to analyze the fundamentals of the turbulence-internal waves interaction, derive the criterion of the threshold of the internal waves generation that fully accounts for the spectral anisotropy, and derive the dispersion relation for internal waves with turbulence. A closure assumption is then introduced relating the renormalized param- eters to global flow characteristics such as the gradient Richardson number (Ri) or local Froude number. Anisotropic turbulent Prandtl numbers are compared with lab- oratory and numerical experiments. The agreement is good in the entire range of Ri, from very small to large indicating that our model captures the physics of strongly stratified turbulent flows. This result has immediate application value for modeling of atmospheric and oceanic boundary layers.
|Original language||English GB|
|State||Published - 2002|