B214 壁乱流の渦群構造の維持・生成に関する研究

概要

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Turbulent channel flows at Reynolds number Re_γ=395 is simulated by DNS (Direct Numerical Simulation). In the comparatively high Reynolds number flow, vortex group which means densly populated elementary vortices are formed in the log-law region. While it is not enough to be undestood their role in turbulence activity and the cycle of generation / regeneration of vortex group. To make clear th mechanism, large scale flow related to the formation of the vortex group is considered. Then POD (Proper Othogonal Decomposition) is applied to extract the large scale flow. In the present simulation, the large scale flow is defined as the sum of top ten mode in which it is arranged in the order concerning the strength of turbulence enegry. Visulaizung the flow structure, it is confermed the existance of large scale streaks and coherent vortex which is elongated for streamwise direction. Especially, since these large scale vortex is similar to a quasi-streamwise vortex found in near-wall region, it is suggested that peculiar mechansim contributing to the generation cycle exists in the large scale flow.
日本流体力学会の論文
2001-07-31