抄録
The influence of transverse vorticity on the dissimilarity between turbulent heat flux and Reynolds stress was investigated by use of direct numerical simulation for two-dimensional channel flow. It is shown that the negative correlation R between wall-normal velocity and pressure gradient fluctuation has an important effect on the dissimilarity. The correlation R would be strongly related to the transverse clockwise vortex in the turbulent flow field. The numerical results show that the correlation R increases and the strength of dissimilarity 5 (turbulent heat flux minus Reynolds stress) decreases as the transverse vorticity shifts to positive The dissimilarity would be mainly caused by the reduction of Reynolds stress near the vortex region, where the velocity fluctuation in the flow direction is accelerated (or decelerated) during fluid particle motion on the ejection (or sweep) side due to the pressure gradient. When an external force is imposed to reinforce the clock-wise vortex, the turbulent Prandtl number Prt is calculated. The numerical results show that Prt is remarkable reduced in the region where the clock-wise vorticity is strengthened.
