CALCULATION OF THE HYDRODYNAMIC FORCES ACTING ON A HYDROFOIL

Characteristics of a hydrofoil have been treated using the lifting surface theory or the vortex lattice method and the wavemaking resistance theory, which need very complicated calculations. But these methods can not directly predict the pressure distribution on the hydrofoil with thickness. This paper presents a method to calculate the flow around the hydrofoil and the hydrodynamic forces acting on the hydrofoil using the thick wing theory and the Rankine source method. Thick wing is represented by the source distribution on the hydrofoil and the vortex distribution on the chord. The strength of these singularities are obtained from the boundary condition on the hydrofoil and the Kutta's condition. In order to represent the wave flow, the source distribution is set on the still water surface so as to satisfy the Dawson's double-model linearised free surface condition. Since the flow field is calculated using these singularities, the pressure distribution, the lift and drag on the hydrofoil are obtained easily. As the numerical examples, we show the wave profiles or the wave contours, the pressure distributions and comparison of the lift and drag coefficients of the 2-D hydrofoils (NACA 0009 and NACA 0012) and the 3-D hydrofoils (NACA 64, A 412, Aspect Ratios of 4 and 10) between calculated and experimental results.