DNS OF TURBULENT HEAT-TRANSFER IN CHANNEL FLOW WITH LOW TO MEDIUM-HIGH PRANDTL NUMBER FLUID

The direct numerical simulation (DNS) of the turbulent heat transfer f or various Prandtl numbers ranging from 0.025 to 5 are performed to ob tain statistical quantities such as turbulent heat flux, temperature v ariance and their budget terms. The configuration is the fully develop ed channel flow with uniform healing from both walls. The Reynolds num ber based on the friction velocity and the channel half width is 180. Turbulent Prandtl number Pr-t is independent of Pr except for Pr < 0.1 .The time constant ratio is also obtained and its dependence on the Pr is examined. Budget of wall-normal heat flux shows that the temperatu re-pressure gradient correlation (TPG) is dominant as the destruction term for a larger Pr while the dissipation is for a smaller Pr. The tw o become comparable at Pr = 0.2 for the present Reynolds number. The b udget terms in the transport equation for the turbulent heat flux are visualized and the influence of Pr is discussed. (C) 1998 Elsevier Sci ence Inc. All rights reserved.