Turbulent Boundary Layer in an Adverse Pressure Gradient: Effectiveness of Riblets

摘要

Measurements of skin friction by means of a drag balance and of velocity profiles by means of a hot wire have been carried out in the boundary layer over a fiat plate in a wind tunnel. A convergent/divergent test section produces a moderate adverse pressure gradient in the divergent part. The purpose of the present study is to investigate the characteristics of this boundary layer and to examine the effectiveness of riblets for skin-friction reduction. We find that the mean velocity follows a logarithmic profile that is shifted downward with respect to the logarithmic law for a zero-pressure-gradient boundary layer.