Near wall measurements in rough surface turbulent boundary layers

Near wall measurements using 2-D LDA have been performed for the mean velocity and Reynolds stresses over smooth and rough surfaces at 11 streamwise measurement locations. This allows for the calculation of the skin friction coefficient using the Navier-Stokes equations with an accuracy of 3-5%. It was found that the destruction of the viscous stress near the wall with increasing roughness led to reduced Reynolds number dependence in the flow field. In addition, it will be shown that a significant reduction in the near wall peak of the streamwise Reynolds stress was seen with increased roughness.