Pre-swirl fins design for improved propulsive performances: application to fast twin-screw passenger ships

Pre-swirl fins-based energy saving devices (ESDs) have been designed to improve the propulsive performances of twin-screw ships. To this aim, a combined BEM/RANSE method for efficient self-propulsion prediction is required. The approach is included in a framework for a design by optimization, where systematic variations of the ESD geometry have been used to explore the design space and maximize the energy-saving effect of the device. Surrogate models based on Ordinary Kriging are used too, with the aim of realizing an affordable design workflow for the very preliminary design of such devices. The results show encouraging improvements that reach promising energy-savings up to 3% at the design point and satisfactory savings also in off-design functioning conditions.