Rim driven propellers: Optimization based design approach using RANS calculations

RIM driven propellers represent an unconventional, but underrated, propulsive solution which hydrodynamic design is still not obvious. In the last years, most of the attention has been devoted to the efficient coupling with electric motors, since only recently the development of permanent magnets allowed for the successful embedding of the driver directly inside the surrounding duct. From the hydrodynamic point of view, however, analysis and, in particular, design strategies are not yet ripe. In the light of the development of advanced design approaches for unconventional geometries, we propose a Simulation-Based Design Optimization tool based on RANS analyses of parametrically described geometries as a part of an automatic, multi-objective optimization loop. The SBDO is used to design a RIM driven propeller with an accelerating type duct, with improved performance simultaneously in terms both of efficiency and cavitation inception at different (design and quasi-bollard pull) functioning conditions.