京都大学 · 工学
Xiuzhong Shen教授の研究室では、乱流のスケーリング則や局所的等方性の妥当性を、風洞実験を用いて高分解能で解明しています。特に、平均せん断流れ下における速度フラクチュエーションの高次モーメントや構造関数のスケーリング指数の Reynolds 数依存性を精密に測定しています。低〜高Reynolds数領域での比較から、乱流の自己相似性や非平衡性の理解を深めることを目的としています。
Figures are computed from collected data and may differ slightly.
The postulate of local isotropy (PLI) is tested in a wind tunnel uniform shear flow in which the Reynolds number is varied over the range 100⩽Rλ⩽1, 100(6.7×102⩽Rl⩽6.3×104). The high Rλ is achieved by using an active grid [Mydlarski and Warhaft, J. Fluid Mech. 320, 331 (1996)] in conjunction with a shear generator. We focus on the increments of the longitudinal velocity fluctuations in the direction of the mean shear. PLI requires that odd order moments of these quantities approach zero as Rλ→∞.
The scaling exponents of the longitudinal structure function, 〈Δuxn〉 and two different transverse structure functions: the longitudinal velocity, u, measured in the transverse, y direction (the direction of the mean shear), 〈Δuyn〉, and the transverse velocity v, measured in the flow direction, x, 〈Δvxn〉, up to n=8, are studied in an approximately uniform shear flow [Shen and Warhaft, Phys. Fluids 12, 2976 (2000)], as well as in decaying (shearless) grid turbulence. Results, for low Reynolds numb
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