Prediction of cavitating performance of a tip loaded propeller and its induced hull pressures

A numerical method solving for the diffraction potential on the hull is coupled with a boundary element method (BEM) to evaluate the propeller-induced hull pressures. The BEM is first implemented for the hydrodynamic analysis of non-cavitating/cavitating propellers in the absence of the hull, and the predicted solutions are taken as the known unbounded potentials in the hull pressure calculations. A tip loaded propeller (TLP) is adopted as the model propeller and mounted under the flat hull subject to uniform inflow. The TLP is operated close to the hull so that infinite speed of sound can be assumed, reducing the frequency domain Helmholtz equation to Laplace's equation which can be solved by a BEM solver. Unsteady sheet cavitation and developed tip vortex cavitation are predicted on the propeller by the hydrodynamic BEM and considered in the calculation of the hull pressures. Several loading conditions are imposed on the propeller and the corresponding pressure predictions and cavitation patterns are compared to published experimental data and to those from unsteady full-blown Reynolds-averaged Navier-Stokes (RANS) simulations. Very good agreement is achieved between the predicted and measured results, especially under moderately loaded condition.