Modulation of the local mass and heat transfer of turbulent double-diffusive convection under stable thermal stratifications

Abstract

We report on numerical studies of bounded double-diffusive turbulent convection, which involves the combined effects of concentration/solutal and thermal buoyancy forces. Our study focuses on an intermediate range of the characteristic non-dimensional numbers, specifically $10^7\le {\mathrm{Ra}}_c\le 10^9$, and $0\le {\mathrm{Ra}}_{\theta }\le 10^6$. We use fixed values for the concentration and temperature Prandtl numbers (i.e. ${\mathrm{Pr}}_c=700$, ${\mathrm{Pr}}_{\theta }$ = 7), which approximately correspond to seawater properties. We apply wall-resolved Large Eddy Simulations (LES) and compare the obtained results with available Direct Numerical Simulations (DNS) in the literature. Our findings show an overall good agreement in predicting the global wall mass and heat transfer coefficients, achieved with significantly reduced computational costs. Furthermore, the local mass and heat transfer distributions reveal a high sensitivity to the strength of the vertically imposed stable thermal stratification. Finally, we present the vertical profiles of the long-term time-averaged first and second moments.