DNS of Stable Spatially-Developing Turbulent Thermal Boundary Layers under Weak Stratification

Abstract

Direct Numerical Simulations (DNS) of spatially-developing turbulent thermal boundary layers under stratification are performed. It is well known that the transport phenomena of the flow is significantly affected by buoyancy, particularly in urban environmentswhere neutral, stable and unstable atmospheric boundary layers are encountered. In the present investigation, the DynamicMulti-scale approach (DMA) by Araya et al. [3] for turbulent inflow generation is extended to thermally stratified boundary layers. Furthermore, the proposed DMA is based on the original rescaling-recycling method by Lund et al. [12]. The two major improvements are: (i) the utilization of different scaling laws in the inner and outer parts of the boundary layer to better absorb external conditions such as inlet Reynolds numbers, streamwise pressure gradients, buoyancy effects, etc. ([4]), (ii) the implementation of a dynamic approach ([3]) to compute scaling parameters from the flow solution without the need of empirical correlations for the friction velocity and friction temperature as in Lund et al. [12] and Kong et al. [11], respectively.