Prediction of sway force and yaw moments of slender ships

A method based on the slender body theory was developed to calculate the sway force and yaw moment on a slender ship performing drifted forward motion. The force and moment were considered to be caused by the purely potential flow around the ship and the vortex shedding from the ship bilge corner. Source elements and discrete vortices were used to represent the sections of the ship hull, and a vortex shedding model was adopted to simulate the shedding and convection of vortices. Calculations were conducted for three different ships and the results were compared with PMM tests. The comparison showed reasonable agreement between the calculated and measured sway forces. For the yaw moment, the agreement between the calculation and the measurement varies notably with the shape of ships