A SECOND TURBULENT REGIME WHEN A FULLY DEVELOPED AXIAL TURBULENT FLOW ENTERS A ROTATING PIPE

When a fluid enters a rotating circular pipe a swirl boundary layer with thickness of (delta) over tilde (S) appears at the wall and interacts with the axial momentum boundary layer with thickness of (delta) over tilde. We investigate a turbulent flow applying Laser-Doppler-Anemometiy to measure the circumferential velocity profile at the inlet of the rotating pipe. The measured swirl boundary layer thickness follows a power law taking Reynolds number and flow number into account. A combination of high Reynolds number, high flow number and axial position causes a transition of the swirl boundary layer development in the turbulent regime. At this combination, the swirl boundary layer thickness as well as the turbulence intensity increase and the latter yields a self-similarity. The circumferential velocity profile changes to a new presented self similarity as well. We define the transition inlet length, where the transition appears and a stability map for the two regimes is given for the case of a fully developed axial turbulent flow enters the rotating pipe.