A Calculation Method for the Lifting Potential Flow around Yawed Surface-Piercing 3-D Bodies

A method especially developed for investigating hulls and keels of sailing yachts at an angle of attack is described. The method may be considered to be an extension of the Hess panel method for lifting, unbounded potential flows to include the effect of the free surface, which may play an important role in the optimisation of the design. The free surface is taken into account in the manner suggested by Dawson, i.e. not only the hull, but also part of the free surface, is covered by panels. However, rather than using double model streamlines on the surface for defining the panels, a user-specified body-fitted grid is employed. Lift is generated by distributing doublets on the lifting pars and this distribution is determined so as to satisfy the Kutta condition at the trailing edge. Test calculations show that the method may be a very useful design tool, although some care is needed to avoid the free surface grid dependence problem.