Direct simulation of stable stratified homogeneous turbulent shear flows
Abstract
The method of the direct numerical simulation is used to integrate the exact timedependent threedimensional NavierStokes and temperature equations for a homogeneous turbulent flow with moderate Reynolds numbers possessing uniform gradients of the mean velocity and of the mean temperature. Hot ascending and cold descending eddies occur in the stably stratified high Prandtl number flow at positions with large positive or negative temperature fluctuations. These eddies create a mean countergradient vertical heatflux. Growing gravity waves force these eddies into a twodimensional horizontal form where they degenerate to fossil turbulence. The validation of existing models of the correlations of the pressurestrain and the pressuretemperature gradients is investigated for flows with strongly stable stratification. It is shown that the dissipative timescale ratio is inversely proportional to the molecular Prandtl number of the fluid and reacts very sensitively on influences of shear and buoyancy forces. Coherent vortex structures break into small scale, weakly inclined vortices when the shear flow is stronglystable stratified.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1988
 Bibcode:
 1988PhDT........21G
 Keywords:

 Shear Flow;
 Simulation;
 Stratified Flow;
 Counterflow;
 Flow Characteristics;
 Fluid Dynamics;
 Heat Flux;
 NavierStokes Equation;
 Turbulent Flow;
 Fluid Mechanics and Heat Transfer