Miscellaneous Topics

In this chapter, the following is shortly dealt with: A much used method for simulating roll motions of ships, which treats surge, roll, and the coupling of roll with the other four kinds of motion nonlinearly, while these other motions themselves are linearized, using pre-calculated transfer functions. The method uses the extremely fast method by Grim to determine the heel restoring moment in waves from previously computed results. The above method is extended to damaged ships by simulating the in- and outflow of water through openings and the water motion within ship compartments and on deck, using special methods for (a) extremely shallow and (b) deeper flooded compartments. Nonlinear motions of planing boats in waves are simulated by extensions of the classical Wagner method developed already about 1930 for waterplane starting and landing. Mathematical quantities (“perturbators”) and their operations are constructed to simplify both the derivation and the programming of second-order formula, e.g., for drift forces and springing excitation. For passenger transport, often the occurrence of sea sickness must be reduced as much as possible. An ISO norm for estimating the frequency of occurrence is sketched and evaluated for normal catamarans and those with longitudinally staggered hulls (“weinblums”). The weinblums have not only less resistance, but are also less prone to sea sickness. A three-dimensional numerical method to predict sloshing in partially filled tanks and swimming pools excited by ship motions is presented.