Dependence of Turbulence-Related Quantities on the Mechanical Forcing for Wind Tunnel Stratified Flow

Wind tunnel experiments of thermally stratified flows are analyzed with the objective of determining the influence of the thermal stratification on turbulence-related quantities. The experimental apparatus consisted of an aluminum plate inserted at the bottom surface of the wind tunnel test section. In order to create a thermally stratified layer, the plate was cooled down to 5ºC and the air entering the tunnel was kept at approximately 20ºC. As the wind speed increases, such stable layer was soon destroyed. Data shows that quantities such as temperature, variances, dissipation rates and turbulent fluxes are substantially reduced when surface cooling is present and that such a reduction is enhanced for weak wind conditions, as these are cases that preserve the stratification. On the other hand, third and fourth order statistical moments, as well as the mean wind speed are much less affected by the stratification.