Experimental Study of LES Models in Turbulent Stratified Flows

Stratification caused by density difference leads to significant changes of flow structure. To achieve accurate and realistic results of stratified turbulent flows in large-eddy simulation (LES), the the behavior of subgrid-scale (SGS) models is crucial. In this study, two-dimensional high resolution velocity and scalar (density) dataset from a turbulent stratified jet, obtained through applying a combined Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) technique, is used to study the behavior of SGS models. A strong correlation between SGS stress and scalar flux is observed. In particular, variations of turbulent Prandtl number in stable stratification and unstable stratification regions are explored from the experimental data.