EVALUATION OF REYNOLDS STRESS CLOSURE FOR TURBULENT BOUNDARY-LAYER INTURBULENT FREESTREAM

Calculations for the interaction of grid-generated freestream turbulen ce with a turbulent boundary layer using the Gibson-Launder Reynolds s tress model are presented. Based on detailed comparisons to experiment al data, it is found that the Gibson-Launder model in general gives go od predictions of friction drag and momentum and displacement thicknes ses, but not of the boundary-layer thickness. Experimentally observed trends in turbulent and mean profiles as a function of the freestream turbulence intensity and the ratio of the free-stream length scale to the boundary-layer thickness are also generally well predicted. It is identified, however, that the Gibson-Launder model does not properly a ccount for the effect of the wall, resulting in the normal turbulent s tress being attenuated at too great a distance from the wall. It is al so observed that, when the conventional gradient diffusion model is us ed for third-order correlations, the calculations underpredict experim ental results and the contribution of turbulent diffusion. Implementat ion of improved formulations for both turbulent diffusion modeling and the wall-reflection term in the pressure-strain model result in impro ved predictions of experimental data.