低レイノルズ数における加熱水平正方形ダクトの二次流れと乱流構造(安定性・乱流乱流(2),一般講演)

概要

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Direct numerical simulations of fully developed low-Reynolds-number turbulent flow in a horizontal square duct heated from below are performed at Richardson numbers 0≤Ri≤1.03 to investigate the buoyancy effects on the coherent structures near the walls, i.e. streamwise vortices and associated streaks, and on turbulence-driven secondary flow of Prandtl's second kind. It is found that cross-streamwise thermal convection which is represented by single large-scale circulation appears to affect the coherent structures and the mean secondary flow for Ri≳0.025. As Ri is increased, the near-wall coherent structures are observed to appear more frequently in the region near one of the two corners on the wall, since they are swept along the wall towards the corner by the large-scale convection. The localization of the near-wall structures affects the profile of skin friction and heat transfer rate on the wall.
2009-09-02