乱流場における運動量と熱輸送の非相似性に及ぼすスパン方向渦度の影響

概要

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The influence of transverse vorticity on the dissimilarity between turbulent heat flux and Reynolds stress was investigated by use of direct numerical simulation data for a channel flow. The theoretical relations regarding to Reynolds stress obtained from Lagrangian momentum equation shows that the correlation v(∂p/∂x) between wall-normal velocity v and streamwise pressure gradient fluctuation (∂p/∂x) has an important effect on the dissimilarity. The correlation v(∂p/∂x) would be negative near the transverse clockwise vortex in the flow field because v and (∂p/∂x) have a different sign to each other around the vortex. The numerical results of turbulent flow and temperature field demonstrate a strong correlation between the strength of dissimilarity (difference between turbulent heat flux and Reynolds stress), -v(∂p/∂x) and the transverse clockwise vorticity. The dissimilarity would be mainly caused by the reduction of Reynolds stress near the vortex region, where the streamwise velocity fluctuation of fluid particle is accelerated (or decelerated) on the ejection (or sweep) side due to the pressure field around the vortex. The strength of dissimilarity increases remarkably where the ring-shaped vortex stands up from the wall and bends to the spanwise direction in the lag-law region.
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