Theory and Procedure for Determining Loads and Motions in Chine-Immersed Hydrodynamic Impacts of Prismatic Bodies

摘要

A theoretical method is derived for the determination of the motions and loads during chine-immersed water landings of prismatic bodies. This method makes use of a variation of two-dimensional deflected water mass over the complete range of immersion, modified by a correction for three-dimensional flow. Equations are simplified through omission of the term proportional to the acceleration of the deflected mass for use in calculation of loads on hulls having moderate and heavy beam loading. The effects of water rise at the keel are included in these equations. In order to make a direct comparison of theory with experiment, a modification of the equations was made to include the effect of finite test-carriage mass. A simple method of computation which can be applied without reading the body of this paper is presented as an appendix, along with the required theoretical plots for computation of loads and motions in chine-immersed landings. Comparisons of theory with experiment are presented as plots of impact lift coefficient and maximum draft-beam ratio against flight- path angle and as time histories of loads and motions. These comparisons cover angles of dead rise of 0 deg and 30 deg, trims up to 45 deg, flight-path angles up to 90 deg, and beam-loading coefficients from 1 to 36.5. Fair agreement is seen to exist over these ranges. The comparisons show in general that the concept involving the two-dimensional deflected mass and a three-dimensional- flow correction can be used to predict accurately the loads and motions in landings of prismatic bodies involving immersion of the chines.