Roughness Effects on the Flow along an Enclosed Rotating Disk

Roughness effects on the three-dimensional boundary layer flow along an enclosed rotating disk have been studied theoretically and experimentally as well as the admissible roughness. The results show that an increase of roughness of the rotating disk results in an increase of core rotation and then in a considerable increase of pressure drop toward the disk centre, that an increase of roughness of the chamber wall has reverse effects, and that the equal roughness of both walls makes the flow almost same as one along smooth surfaces. The theoretical results based on the logarithmic velocity distributions show good agreement with the measurements. The well-known formula of admissible roughness in the two-dimensional flow is confirmed to be effective even in the three-dimensional boundary layer flow, because the secondary flow has little effect on the flow in the immediate vicinity of the wall and then the viscous sublayer is not influenced so much.