Propeller Performance Prediction in an Artificially Generated Wake Field Using RANSE

Marine propellers usually operate behind a ship and are subject to a non-uniform inflow field due to the ship’s boundary layer and wake system. This flow field is responsible for unsteady loads on the blades and often for the occurrence of unsteady cavitation phenomena, which are important in the analysis of shaft vibrations and pressure fluctuations. RANSE (Reynolds-Averaged Navier-Stokes Equations) solvers are becoming a widely used tool for the modelling of the unsteady flow around propellers operating behind a ship. However, RANSE solvers are also associated with large computational requirements. Mikkelsen et al. (2007) introduced a method using body-forces for the generation of the ship wake field. These body-forces were combined with RANSE for the prediction of the propeller performance without the presence of the ship hull, reducing substantially the computational cost. A similar method was implemented by Shin et al. (2011) for unsteady cavitation simulations. These results have shown the feasibility of the method for the generation of a desired ship hull wake and prediction of the blade-load variations. The aim of the present paper is to present a method for an accurate prediction of the propeller unsteady performance in an artificial wake field using RANSE in a cost-effective way. The propeller performance predictions in this artificial wake field are compared to the predictions in behind the ship. The paper is organised as follows: the major features of the numerical method are presented in Section 2; the test case and numerical set-up are described in Section 3; the numerical results are shown in Section 4; in Section 5 the main conclusions are drawn.