Effects of Density Stratification on Turbulence Structures and Turbulent Heat Transfer Mechanism in Turbulent Open-channel Flows

摘要

This study investigates an effect of density stratification on turbulence structures and turbulent heat transfer in a turbulent flow with a free surface. A direct numerical simulation (DNS) technique is applied for this purpose to fully developed turbulence in an open channel. Both positive and negative temperature differences between the bottom wall and the free surface are introduced to impose both stable and unstable density stratification. Fully-developed turbulence statistics are evaluated to elucidate the effects of density stratification on both turbulence structure and turbulent heat transfer processes near the free surface.