An Experimental Investigation of Parametric Rolling in Head Waves

Abstract

In this paper, the possibility of excitation of parametric rolling on a ship advancing in head sea condition is studied on an experimental basis. The excitation of parametric rolling was effectively observed in the experimental tests, together with some case of capsizing. The parametric rolling exhibited the typical subharmonic behavior. The use of classical Mathieu equation theory, coupled with hydrostatic calculations in longitudinal waves, accounting for both vertical motions and wave effect on stability, allows a satisfactory explanation of the observed phenomena. In addition, the problem of determination of roll damping dependence on ship speed was solved by using roll decay tests in calm water with forward speed. A simplified nonlinear modeling was proposed to account for the roll motion amplitude above threshold. The comparison with the experimental results is reasonably good.