Hydrofoil supported sailing vessels gained more and more importance with in the last years. Due to new processes of manufacturing it is possible to build slender section foils with low drag coefficients and heave stable hydrofoil geometries are becoming possible to construct. These surface piercing foils often tend to ventilate and cavitate at high speeds. The aim of this work is to define a setup to calculate the hydrodynamic forces on such foils with RANSE CFD and to investigate whether the onset of ventilation and cavitation can be predicted. Therefore a surface piercing hydrofoil of an A-Class catamaran is simulated by using the RANSE software FineMarine with its volume of fluid method. The C-shaped hydrofoil is analysed for one speed at Froude Number 7.9 and various angles of attack (AoA). The rake was defined and a leeway angle was applied to simulate realistic set ups. It is presented how the rake and drift angle influence the lift to drag ratio. Over a wide range of AoA there is no ventilation predicted but cavitation may occur from AoA > 10°. Due to the very small aspect ratio (Λ=2.64), the maximum AoA before stall is increased. The simulations have been verified by extensive analyses, including domain size verification for unrestricted water, mesh refinement and y+ verification. The influence of the K27 (cavitation tunnel of the Technical University of Berlin) on the flow around the hydrofoil and the wave system is presented. It is shown how test section of the K27 influences the flow around the foil, the forces and the wave elevation. Finally the CFD results are compared against the experiments conducted in the K27.

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