Abstract
Turbulent structure in a boundary layer developed over two different types of three-dimensional rough walls, namely, cavity and protrusion has been investigated to understand effect of the geometrical feature on turbulent statistics. Experiments were made under the zero pressure gradients with constant free stream velocity of 7m/s. Over the protrusion type of rough wall, the local skin friction coefficient Cf is much larger than those of d-type and cavity type rough wall flows. As R_θ increases, the local skin friction coefficient tends to almost the same value over d-type and cavity type rough walls. Deficit in mean velocity profile is the largest over the protrusion type and takes almost the same over the cavity and d-type rough walls. Certain differences corresponding to the geometrical feature are observed near wall and around outer edge of boundary layer in skewness profile of S(ν)
