Effect of a Short Roughness Strip on the Near Wall Reynolds Stress Anisotropy Tensor in a Turbulent Boundary Layer

Hot-wire measurements have been carried out in a turbulent boundary layer subjected to an impulse in form of a short roughness strip with a view to examine it effect on the near-wall Reynolds stress anisotropy tensor. The result indicates that, relative to smooth wall, the anisotropy of the Reynolds stress tensor is modified downstream of the roughness strip. For example, the anisotropy of the near-wall flow is decreased, and the flow shows a closer tendency towards isotropy than the smooth wall near the wall region. The roughness strip acts in such a way as to change the magnitude of the smooth wall data without necessary altering the wavelength of the variation.