On Motions of a High Speed Planning Boat in Regular Head Sea

Abstract

Recent advances in the research of ship motion in a seaway have enabled to predict the ship motion. These researches, however, are restricted to those of displacement type ships such as a merchant ship and a destroyer, and as to behaviours of high speed planing boat in a seaway few available researches have been published.In the present study the towing tank test of a torpedo boat model was carried out in regular head wave and experimental data were discussed along with the results calculated by Ordinary Linear Strip Method (O. S. M.).The conclusions deduced from these studies are as follows, 1) High frequency components appear in pitching and heaving oscillations at higher encounter frequency, that is, at higher speed and shorter wave. In these regions, each mean value of the pitching and heaving oscillation becomes larger compared with the trim angle and vertical displacement in still water.2) The motions calculated by the O. S. M. give good agreement with experimental data for Fn< 0.5, but they do not always for higher Froude number.3) In spite of much higher frequency components in the motions, the amplitudes of pitching and heaving motions are almost proportional to those of the wave, that is, the linearity to wave height is nearly conserved.