Slamming Due to Pure Pitching Motion

摘要

A method is developed for predicting maximum slamming forces experienced by a ship's hull when its impact with the free water surface is due to pure pitching motion. The results of the theoretical investigation are compared with those obtained from a series of experiments performed upon an eight-foot model of the MS SAN FRANCISCO, in which the model is given an initial angular displacement about a fixed axis of rotation about 30 percent of the length from aft, and allowed to pitch in her natural period. The results are given in the form of theoretical and experimental acceleration traces. The pressure distribution over some of the forward sections is also obtained theoretically, and the total moment due to slamming is estimated both from this and from the differential equation of slamming. In the case of pure pitching motion about this axis, the general location of the region of high pressure at the time of slamming is found to be about 20 percent aft of the forward perpendicular. The effect of slamming on the pitching motion of the ship is shown to be very slight. The effect on slamming on finite speed of advance, for the case of an artificially pitched model moving through calm water, is also very small. (Author)