Mean Flow Quantities for the Turbulent Boundary Layer over an Equivalent Smooth-Mesh Rough Wall.

Abstract

Mean flow quantities have been investigated experimentally for the turbulent boundary layer developing over an equivalent smooth-mesh rough wall. The roughness Reynolds number defined as ratio of the roughness height to the viscous length is about 4 which corresponds to the fluid dynamical smoothness. Measurements were made within Reynolds number range of about 2200 to 6000. Mean velocity profile nondimensionalized by outer variables shows a similarity within all Reynolds numbers tested, but the present mean velocity profile increases in the inner layer compared with the smooth wall flow. The value of the local skill friction coefficient evaluated using five different methods was slightly lower than the value for smooth wall flow. For the present mesh wall flow, both logarithmic velocity and velocity defect laws are applicable, and the inclination of logarithmic linear part, namely Karman constant, is the same as for smooth wall boundary layer.