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

A new asymptotic method is applied to the analysis of roll decrement d ata which can determine nonlinear damping coefficients from large-ampl itude roll motions. The roll restoring moment can be strongly nonlinea r. The accuracy of the method is assessed by rolling with an initial a mplitude, using given nonlinear equations of motion. The difference be tween the input and predicted damping coefficients will demonstrate th e applicability of the analysis method. Using an iterative correction procedure, accurate coefficients can be obtained for large rolling ang les up to the amplitude at the maximum value of the restoring moment.