遷移粗さおよび完全粗面領域におけるｄ形粗面境界層の組織構造

望月 信介, 大坂 英雄

doi:10.1299/kikaib.58.1392

遷移粗さおよび完全粗面領域におけるｄ形粗面境界層の組織構造

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書誌事項

タイトル別名

Coherent Structure of a d-Type Rough Wall Boundary Layer in a Transitionally Rough and a Fully Rough Regime.
センイアラサオヨビカンゼンソメンリョウイキニオケル dガタソメ

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抄録

The Reynolds number effect on the turbulent structure of a d-type rough wall turbulent boundary layer was studid experimentally in terms of the coherent structure. Mean bursting frequency, conditional averaged velocity signals and fractional contribution of the stress-generating motions were obtained with both the VITA method and the four-quadrant analysis, respectively. The effect of the three parameters, namely, bulk Reynolds number R_θ, roughness Reynolds number and friction parameter u_τ/U₁, were considered in the present study. Even scaled with the inner, outer and mixed variables, the nondimensional bursting frequency depends on the Reynolds number. The relative magnitude of fractional stress contribution of ejection to that of sweep increases with decreasing Reynolds number.