ESTIMATION OF NONLINEAR DAMPING COEFFICIENTS FROM LARGE-AMPLITUDE SHIP ROLLING MOTIONS

A new asymptotic method is applied to the analysis of roll decrement data which can determine nonlinear damping coefficients from large-amplitude roll motions. The roll restoring moment can be strongly nonlinear. The accuracy of the method is assessed by rolling with an initial amplitude, using given nonlinear equations of motion. The difference between the input and predicted damping coefficients will demonstrate the applicability of the analysis method. Using an iterative correction procedure, accurate coefficients can be obtained for large rolling angles up to the amplitude at the maximum value of the restoring moment.