Mixing in a stratified shear flow: Energetics and sampling
Abstract
Direct numerical simulations of the time evolution of homogeneous stably stratified shear flows have been performed for Richardson numbers from 0 to 1 and for Prandtl numbers between 0.1 and 2. The results indicate that mixing efficiency R(sub f) varies with turbulent Froude number in a manner consistent with laboratory experiments performed with Prandtl numbers of 0.7 and 700. However, unlike the laboratory results, for a particular Froude number, the simulations do not show a clear dependence on the magnitude of R(sub f) on Pr. The observed maximum value of R(sub f) is 0.25. When averaged over vertical length scales of an order of magnitude greater than either the overturning or Ozmidov scales of the flow, the simulations indicate that the dissipation rate epsilon is only weakly lognormally distributed with an intermittency of about 0.01 whereas estimated values in the ocean are 3 to 7.
 Publication:

Annual Research Briefs, 1992
 Pub Date:
 January 1993
 Bibcode:
 1993arb..nasa..335I
 Keywords:

 Computational Fluid Dynamics;
 Computerized Simulation;
 Mixing Length Flow Theory;
 Shear Flow;
 Stratified Flow;
 Turbulent Flow;
 Energy Dissipation;
 Froude Number;
 Prandtl Number;
 Richardson Number;
 Turbulence;
 Fluid Mechanics and Heat Transfer