Ship roll damping moments

Abstract

In the paper a nonlinear form of the ship’s roll damping moment and an equivalent linear damping moment is introduced. By comparison of the action of both moments during one quadrant of the roll period an expression was found linking the equivalent linear damping moment with the nonlinear roll coefficient. The equivalent linear roll damping moment coefficient can be calculated from model tests on the basis of the roll decay characteristics. Presented are also exemplary calculations of the nonlinear roll damping coefficients for a model of the passenger ferry POLONIA. Their results are given in a graphical form.