Hydrodynamic Analysis of Dynamically Positioned Vessels

A method for the prediction of vertical ship motions in shallow water has been developed. In this method 3 contributions to the vertical motions are distinguished viz. an average part, a low frequency part related to wave grouping and a part related to individual wave action. Calculation procedures for each of the parts are presented and validated against model tests.In this paper a calculation method for ship motions in shallow water is presented. This method enables exploration of the effects of forward speed wave characteristics; and heading on the vertical motions of a ship. For the case of an LNG carrier in shallow water these effects are illustrated with respect to the vertical motions at the keel. See Figure 27. From the figure it is concluded tentatively that the effects of forward speed may not be neglected.