Modeling of transient hydrodynamic lifting forces of sailing yachts and study of their effect on maneuvering in waves

The calculation of hydrodynamic lifting forces sustained by a sailing yacht's hull performing maneuvers in regular incident waves is reported. The mathematical model involves the application of the lifting surface theory for transient flows, implemented through the numerical scheme of the vortex lattice method and corrected for linear thickness effects of the simulated body geometry. The mathematical influence of the waves appears through the derivation of the wave potential and it is employed in a kinematic sense via the introduction of an additional inflow velocity component on the lifting surface. Validation with data derived from experiments in calm water showed very good agreement. Additionally, the variation of the side force coefficient while sailing in waves has been quantified in terms of the amplitude of oscillation due to the wave orbital velocities. The formulation is intended to upgrade the respective computational component in a mathematical model previously developed by the authors, for the maneuvering motions of sailing yachts. Parametric studies of maneuvering and course-keeping demonstrate a sensitivity of the yacht to wave steepness and heading angles, with a deficit in sustaining capacity appearing for lower wind speed.