Dissimilarity between heat and momentum transfer in turbulent plane Couette-Poiseuille flow

Abstract

Turbulent heat transfer in plane Couette-Poiseuille flows has been investigated numerically at Reynolds number Re = 2000 for Prandtl Number Pr=1. In this flow system the lower wall moves at a temporally constant speed U_lower, while the upper wall is at rest. While keeping a volume flux (and so a bulk mean velocity u_b) constant, the lower wall speed is changed in the range of 0 ≤ U_lower/u_b ≤ 2 to establish turbulent Couette-Poiseuille flows. Dissimilarity between heat and momentum transfer is found significantly for a certain value of U_lower, for which the mean velocity gradient on the lower wall is weak enough to be free from vigorous turbulence activity. Only spanwise vortices exist in the near region of the quiescent lower wall to induce the streamwise velocity so that the wall velocity gradient may be weaker, leading to the excess of the wall temperature gradient (or heat flux) over the wall velocity gradient (or skin friction).