Flow in axially rotating pipes

This paper describes the flow pattern, hydraulic resistance, and stability of flows in axially rotating pipes. Developed and undeveloped flows, respectively, were introduced to smooth pipes rotating about their axes, and changes of flow pattern, hydraulic losses, and turbulent fluctuations due to the rotation were measured across sections at various distances from the pipe entrance. The pipe rotation gives two counter effects on the flow: one is a destabilizing effect due to a large shear caused by the rotating pipe wall and the other is a stabilizing effect due to the centrifugal force of the swirling velocity component. The different effects of the pipe rotation on the flow stability are attributable to the flow condition at the inlet section and also to the boundary layer development. The stability effect can be predicted theoretically by use of a relationship between the mixing length and Richardson number proposed by Bradshaw.