Variations on a theme by Dawson - recent improvements of a potential flow calculation method for ships

This paper discusses a few aspects of Rankine source methods for wave resistance calculation, and of MARIN's code DAWSON in particular. Different slow-ship linearization assumptions are compared. Differences in the results are generally small in practice. The use of normal dipoles on the free surface has been investigated but found to be inadmissible. A method to suppress point-to-point oscillations and waves upstream of the bow by a slight upstream shift of collocation points, is described. Lifting surfaces are represented by discrete vortices in the camberplane complementary to the source panels on the boundary. Alternative methods to derive the resistanee by the use of Lagally's law are tested. The pressure integration turns out to be sufficiently accurate provided that the zero Froude number pressure distribution is used as a correction for numerical errors. Practical use of DAWSON is illustrated with applications to a cruiseship and a sailing yacht.