Streamwise Vortical Structure associated with the Bursting Phenomenon in a d-Type Rough Wall Boundary Layer : Conditional averaged velocity signals and velocity vector plots

Three-dimensional spatial structure associated with the bursting phenomenon in a d-type rough wall turbulent boundary layer was investigated with the VITA tecnique. The conditional averaged signals of the three velocity components and the Reynolds shear stress were obtained at 28 locations in the cross stream section. These time dependent data were used to draw velocity vector plots in physical coordinate of x-y and x-z planes. The ejection process is associated with a pair of stremwise vortical motion which spanwise scale is about 50 viscous wall units. The Reynolds shear stress is mainly produced at the symmetrical plane of the vortical motion, z^+=0. While the sweep process is associated with large-scale vortical structure which is characterized by intense spanwise component.