DNS Study on Effect of Prandtl Number for Turbulent Boundary Layer with various External Forces

The object of this study is to investigate the effect of Prandtl number in heat transfer phenomena of turbulent boundary layer with various external forces by means of direct numerical simulation (DNS). In this study, DNS of turbulent boundary layer with an adverse pressure gradient (APG) or a buoyancy is carried out under conditions of three different Prandtl number. In the boundary layer of thermal field which develops in the entrance region due to the boundary condition of wall, the effect of Prandtl number is clearly observed in all cases, though the thermal boundary layer is not fully developed. However, in the case of lower Prandtl number, the effects of APG or buoyancy cannot be much seen. As for the boundary layer of velocity field, it can be slightly observed the effect of Prandtl number due to the undeveloped thermal boundary layer. Therefore, DNSs of this study reveal characteristics and structures of turbulent boundary layer with various external forces in various Prandtl number.