On nonlinear rolling of ships in random seas

Abstract

An analytical method has been developed to obtain an approximate solution to the nonlinear rolling equation of a ship sailing in random waves. The stability of the stationary solution is then investigated by examining the behavior of the solution to the equation of the first variation of the equation of motion.

Results of calculations made for a model of an American Challenger class cargo ship indicate large departures from the linear solution, especially near resonance. These results also indicate that the model may have unstable motion in quartering seas. Although this instability can be eliminated by considering a nonlinear damping form, the motion is still expected to be violent near these headings.