Abstract
A parameter identification method is used to estimate linear damping at natural frequency (at resonance frequency) as a function of wave steepness. An uncoupled nonlinear equation representing roll motion of ships with linear damping and nonlinear restoring moment is used for this purpose. Linear damping is also estimated using analysis of free roll. In order to see if any influence of wave steepness on damping coefficient, responses is calculated with coefficients obtained from parametric estimation method and free roll analysis. Responses obtained with damping coefficient obtained form free roll are in good agreement with experiments irrespective of wave steepness.
