縦リブによるｄ形粗面乱流境界層の抵抗減少の試み　高次モーメント量と条件付解析

望月 信介, 伊澤 明峰, 大坂 英雄

doi:10.1299/kikaib.60.3264

縦リブによるｄ形粗面乱流境界層の抵抗減少の試み　高次モーメント量と条件付解析

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タイトル別名

Turbulent Drag Reduction in a d-Type Rough Wall Boundary Layer with Longitudinal Thin Ribs Placed within the Transverse Grooves. Higher-Order Moments and Conditional Sampling Analysis.
タテリブニヨル dガタソメンランリュウキョウカイソウノテイコウ

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Large-scale coherent motions were investigated experimentally in a d-type rough wall boundary layer modified with longitudinal thin ribs. Higher-order moments and conditional averaged statistics were obtained at R_θ=1300 and 5000, where the local skin friction coefficients of the modified flow are the same with and about 17% larger than that of the smooth wall flow, respectively. The triple velocity correlations are reduced from the near-wall region through the outer edge of the layer by wall modification with longitudinal thin ribs. The higher-order moments and conditional averaged patterns with the VITA analysis show that the turbulence-producing model by means of the streamwise vortical structure and induced intermittent vortex shedding from the roughness grooves are reasonable.