Abstract
Measurement of conditional sampling (Quadrants analysis) and high moment quantities have been performed in the vicinity of a roughness element for the boundary layer over a k-type rough wall, which consists of two-dimensional square ribs arrayed with pitch ratio of 4,having a ratio λ_s of cavity width b to a pitch length λ of 0.75. Comparing with the results of λ_s=0.5 and 0.7,the contribution to the Reynolds shear stress from each event and the vertical turbulent flux of the streamwise turbulent energy and the Reynolds shear stress depend on the wall roughness. In the near wall region influenced directly by a roughness element of λ_s>0.5∿0.7,the sweep event largely dominates to the Reynolds shear stress and the wall ward turbulent motion is revealed from the results of the vertical turbulent flux.
