CFD predictions of unsteady cavitation for a marine propeller in oblique inflow

Abstract

In this paper the Potsdam Propeller Test Case is numerically investigated in oblique inflow conditions. We consider three different topics: open water performance curves, cavitation observations, and pressure pulses induced by the propeller to the ceiling of the cavitation tunnel. In the oblique flow case, the inflow is not uniform from the perspective of the propeller, which results in the dependency of the propeller blade loading and cavitation on the blade rate frequency. The numerical simulations were compared to experimental results for each investigated case. Additionally, we analyzed the unsteady features of the cavitation on the blades as well as the pressure peaks in the propeller wake due to collapsing cavities. We found that the global performance and cavitation patterns close to the blades agree well with the tests in the numerical simulations. The agreement with the tests for the pressure pulses on the tunnel ceiling was better in the non-cavitating case. The unsteady cavitation shed behind the propeller and the subsequent collapse events induced a vast increase in recorded maximum pressure values. Root cavitation collapse produced pressure pulses an order of magnitude greater than the collapse of tip vortex cavitation. Also the collapse of cavities on the blades contributed to a significant increase in the pressure fluctuations on the blades.