Abstract
The article analyses excitations of a multihull vessel using stochastic formulation. The excitations which make the vessel move come from the motion of sea waves and the action of wind. The sea undulation has most frequently the form of irregular waves, and that is why it is assumed in many studies of sea-going vessel dynamics that the undulation process has probabilistic nature. In the article the dynamics of a multihull vessel is analysed using a linear model on which an irregular wave acts. It was assumed that the examined object interacts with the head sea, and for this wave a set of state equations was derived. The head sea provokes symmetric movements of the object, i.e. surge, heave and pitch.