Effectiveness of Nonlinear Roll Damping Formulations on Roll Response in Regular Waves

摘要

Method of multiple scales is used to obtain analytical solution of the nonlinear roll equation and to verify the effective and valid formulation of the nonlinear damping in regular waves. Roll motion is highly nonlinear in nature due to nonlinear damping and restoration moments. There are various forms that are used to represent nonlinear damping moment. In present study, the effect of form of nonlinear damping moment on estimation of roll response of a training ship is investigated. Damping coefficients are estimated from free roll decay curve and hydrodynamic theories. Frequency-response relations obtained with method of multiple scales are used to calculate roll response. Analytical results are compared with roll amplitudes obtained from forced roll experiments in regular beam waves. Results indicate that, damping moment representation has effect on estimation of maximum roll amplitude in regular beam waves.