Quadrant and joint probability density function analyses of high-prandtl number turbulent heat transfer in high-reynolds number channel flows

The effects of the large-scale structure in a channel flow on turbulent heat transfer were investigated by using the high resolution Direct Numerical Simulations (DNS) database. The configuration is a fully developed turbulent channel flow with the constant wall-temperature difference condition. DNS database are the Reynolds numbers based on the friction velocity and the channel half-width of 150, 400, and 1000 and the molecular Prandtl number of passive scalar is 25. Joint probability density function (JPDF) profiles of the Reynolds shear stress and the wall-normal turbulent heat flux are independent of Reynolds number, outside the extent of the impact of the channel center or thermal boundary conditions. Though, a larger contribution of sweep events to both of the Reynolds shear stress and the wall-normal turbulent heat flux on the quadrant analyses, and one of strong turbulent intensities on the JPDF analyses, are founded with increase of Reynolds number. Furthermore, at the buffer layer, contributions of ejection events only to the wall-normal turbulent heat flux are increased with increase of Reynolds number. © 2013 The Japan Society of Mechanical Engineers.