遷移粗さおよび完全粗面領域におけるd形粗面境界層の統計的性質

概要

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In order to investigate the low Reynolds number effects on the turbulent structures of a d-type rough wall boundary layer, the statistical properties in a transitionally rough and a fully rough regime have been examined experimentally. The measurements associated with the turbulent production rate, probability distributions, higher-order moments and energy spectra were made in the range of momentum thickness Reynolds numbers of R_θ=700 to 5140. The local equilibrium state can be recognized for a wide Reynolds number range down to R_θ=700. The probability distributions and the higher-order moments including Reynolds shear stress flux show that the ejection events due to positive high amplitude of υ fluctuating component play a dominant role on the turbulent transport process in the inner layer of the present rough wall flow for a transitionally rough regime of R_θ≦2000. The low Reynolds number effect on the outer layer, which enlarges the contorted surface of the viscous super layer, is found for the Reynolds number range R_θ≦800.
1990-05-25