Model Testing and Numerical Simulations of Seakeeping Performance for High-Speed Vessels

Given the need to support the long distance deployment of men and material, the US Navy has been exploring the engineering limits and capabilities of open ocean operation for high-speed ships. Of great concern are the risks associated with: Ship Motions - Human Factors " " " Ship Dynamic Stability and Manoeuvring Ship Dynamic Loads In order to address these risks, an initial assessment of design tools has been be carried out under the auspices of the Office of Naval Research. The initial goal of this effort was to determine the current state of the art in predicting ship motions of high-speed ships. Under this initiative, the ship motions and loads prediction program, Large Amplitude Motions Program (LAMP), has been evaluated. This program is a time-domain simulation model specifically developed for computing the motions and loads of a ship operating in extreme sea conditions. In order to perform these simulations, LAMP uses a time stepping approach in which all of the forces and moments acting on the ship are integrated in the time-domain using a 4th-order Runge-Kutta algorithm. Specific account of those forces due to the wave-body interaction, appendages, control systems, and green-water-on-deck, are included in the computation at each time step and the 6-degree-of-freedom (DOF) equations of motions. Using the LAMP suite of programs, numerical predictions were made and compared with two sets of model test data. Included among the comparisons were predictions for pitch, roll and heave acceleration in both head and oblique sea conditions.