DNS of turbulent heat transfer in channel flow with respect to Reynolds and Prandtl number effects

The direct numerical simulation (DNS) of turbulent heat transfer in a channel flow has been carried out to investigate the Reynolds and Prandtl number effects on the turbulent heat transport. The configuration is a fully developed turbulent channel flow with uniform heating from both walls. The Reynolds numbers based on the friction velocity and the channel half width are 180 and 395, and the molecular Prandtl numbers are 0.025, 0.2 and 0.71. The statistical quantities such as the temperature variance, turbulent heat fluxes, turbulent Prandtl number and the time scale ratio are obtained and the effects of the Reynolds and Prandtl numbers are examined. Budget terms of the temperature variance and the turbulent heat fluxes are also calculated. In addition, the instantaneous flow and thermal fields are visualized in order to investigate the structures of streaks and vortices. (C) 1999 Elsevier Science Inc. All rights reserved.