片壁面に付加された粗さ要素の粗さピッチ比がチャネル流に及ぼす影響

（空間平均量に基づく調査）

抄録

The effect of roughness pitch ratio for a wall-bounded shear flow has been investigated based on spatial averaging operation of the Reynolds equation for a channel flow. The roughness pitch ratio was PR =1, 2, 4, 8 and 16.The velocity field was measured with 2-D PIV system. The Reynolds number based on the channel height was 2500. The spatially averaged streamwise mean velocity profiles of PR = 4, 8 and 16 were defected compared to those of PR =1 and 2 on a rough wall side. The spatially averaged shear stress profiles for all roughness pitch ratios can be represented as a liner function, and the slope of each linear function varied depending on the local skin friction coefficient. The profile of the spatially averaged Reynolds stresses takes a maximum value at the roughness pitch ratio of 8. The peak value of the dispersive stresses increases with the roughness pitch ratio.