Viscous frictional torque in the flow between two concentric rotating rough cylinders

This paper describes an experimental study of the effects of surface roughness on the flow between two concentric cylinders, one of which rotates. The surface roughness has some effects on the coefficient of viscous frictional torque C M in the transient and in the fully developed turbulent region. In the fully developed rough turbulent flow, the value of C M depends on both the Reynolds number R ω and the relative roughness r m / k in the case where the outer cylinder rotates, but C M depends only on r m / k in the case where the inner cylinder rotates. The effect of the surface roughness of the inner cylinder is greater than that of the outer one for both cases.