RANS simulations of cavitating azimuthing thrusters

Developments of computational power lead to new options for flow field analyses of steerable thrusters. The step from wetted flow RANS to simulations with a cavitation model activated is made. In this way the viscous effects are taken into account, so that vortical structures can be modelled properly. The complex flow phenomena of cavitating thrusters need to be validated against experimental data to evaluate the accuracy. Model scale cavitation tunnel data has been used for validation. It has been recognized that the impact of gravity effects is only correct when Froude scaling is applied. Often the priority is put on higher Reynolds numbers, and therefore the Froude scaling cannot be maintained in the experiments. The flow simulations have been made at full scale, so that both Reynolds and Froude numbers are correct. Initial calculations have been made with uniform inflow, and in second phase the hull geometry has been taken into account to model thruster-hull interaction and proper inflow to the thruster. Results of the full scale simulations have been presented and the impact of the presence of the free surface relatively close to the thruster unit is discussed.