A computational study into the effect of the winglets on the performance of fully submerged hydrofoils

Hydrofoil vessels, which greatly take the advantage of the dynamic lifting force during the cruising, are amongst the watercrafts that can significantly benefit from the application of the winglets. These benefits can be decreasing the lift off speed of the vessel, increasing its maximum speed or reducing the drag force acting on the hydrofoils and hence contributing to fuel saving. This study aims to provide a basic understanding of the benefits of the usage of the winglets for the fully submerged hydrofoils of a marine vessel. In accordance with this purpose, the performance of several winglets, which were generated based on the Withcomb's winglet design, was analysed by means of RANS computations. The effect of the chord length, span, cant angle, trailing edge sweep angle of the winglets and effective span of the hydrofoil/winglet system was systematically investigated. Detailed information about the topological features of the flow around the hydrofoil and winglets were provided. The influence of the flow structure on the performance and generation of the lift was extensively discussed. The computations revealed the effectiveness of the usage of the winglets.