Characteristics of a turbulent boundary layer perturbed by spatially-impulsive dynamic roughness

Statistical and spectral analyses of the manipulation of a canonical zero pressure gradient turbulent boundary layer using static roughness and low-frequency dynamic roughness patches are presented. A shift of spectral energy away from the wall downstream of the roughness patch is observed. The dynamic roughness is shown to disrupt the structure of the boundary layer, while embedding its periodic signature in an extensive stretch of the downstream flow field.