Optimization of podded propulsor for fast ropax using RANS solver with cavitation model

Within EU Project FASTPOD the application of podded propulsors to high speed commercial vessels has been studied. In particular a Ropax and a cargo ship were selected as merchant ship candidates for the near future with speeds in the range of 35-38 knots. For such high speeds the hydrodynamic design of the propeller with its housing is critical due to the appearance of cavitation both on the propeller blades and pod housing. The paper deals with the design process of the propeller and housing for the Ropax vessel using RANS solver FINFLO. A one-phase cavitation model has been implemented, which combines a linearized kinematic boundary condition for the tangentiality of the flow at the bubble surface with a constant pressure boundary condition in the cavitation bubble. The simplicity of the model allows a reasonable prediction of cavitation extent without a significant increase of computational effort. Good performance from a cavitation standpoint both on the strut and propeller blades usually results in reduced propulsor efficiency. For this particular application a compromise is made to get satisfactory performance from both cavitation and efficiency point of view.