THE RELATIVE MOTION BETWEEN SHIPS IN RANDOM HEAD SEAS

Abstract : As part of the Navy's program to develop mobile port facilities, an analytical model was developed which can be used to compute the relative motion between vessels in regular and random head seas. The model, based on strip theory, is suitable for analyzing all single hull, linearly moored slender vessels. Since symmetry of moorings (if present) is assumed throughout, the motion is restricted to heave, surge and pitch. Deep-water added mass and damping coefficients are used in the equations of motion, and the resulting model predictions are considered valid provided that the draft-to-mean depth ratio does not greatly exceed 0.50. Typical results from the analysis are presented. These include graphs and tables of: the relative horizontal and vertical motion between two moored ocean-going vessels in shoal water, the relative horizontal and vertical motion between a moored ship and an unmoored beach discharge lighter, and the shoal water surge response of vessels as a function of mooring stiffness. (Author)