A Simple Prediction Formula of Roll Damping of Conventional Cargo Ships on the Basis of Ikeda’s Method and Its Limitation

Abstract

Since the roll damping of ships has significant effects of viscosity, it is difficult to calculate it theoretically. Therefore experimental results or some prediction methods are used to get the roll damping in design stage of ships. Among some prediction methods, Ikeda’s one is widely used in many ship motion computer programs. Using the method, the roll damping of various ship hulls with various bilge keels are calculated to investigate its characteristics. Ship hull forms are systematically changed by changing length, beam, draft, midship sectional coefficient and prismatic coefficient. On the basis of these predicted roll damping of various ships, a very simple prediction formula of the roll damping of ships is deduced. It is found, however, that this formula cannot be used for ships that have higher position of the center of gravity.