Cavitation analyses of trochoidal propellers

Ship’s propulsion efficiency plays a key role in cutting emissions together with other major technological advances in alternative fuel and energy sources, such as batteries and fuel cells. However, the availability and price of energy increases the importance of energy efficiency. Novel propulsion concepts enable achieving higher propulsive efficiencies to reduce fuel consumption and emissions. In this paper we present a hydrodynamic and cavitation study of a high efficiency trochoidal propeller by means of computational fluid dynamics (CFD) methods. This type of propeller features individual flapping foils that rotate around a vertical axis. It works as a bio-mimicking device as the trajectories of the foils simulate the motion of whale or dolphin tails, promoting higher efficiencies of even 20 % or more when compared to conventional screw propeller solutions. To obtain insight into cavitation phenomena and resulting cavitation types of this kind of device, we study hydrodynamic performance for a variety of scenarios, from a non-cavitating state to cavitating conditions. This makes it possible to better understand causes and effects of potential cavitation and, if necessary, minimize it, leading to improved designs.