Efficient Predictions of Wave-Induced Ship Motions for Ship Defence Models

Abstract : This report presents a library of wave-induced ship motion modules for use insimulation applications. The library is intended for ship defence models andother simulation applications requiring robustness, fidelity, and high computationalspeed. Ship motions in long-crested random seaways are determined using ship motion response amplitude operators (RAOs) computed by DRDC Atlantics SHIPMO7 program. The output ship motions are given as perturbations relative to the steady or slowly varying input ship course. Time domain predictionsfrom the library have been verified through comparisons with frequency domain predictions from SHIPMO7, which has undergone extensive validation. The library is available as a Python module and also as a dynamically linked library(DLL) callable from C and other compiled languages. During benchmarking on a 800 MHz Pentium III computer, ship motion predictions required approximately0.002 s per time step, giving performance 50 times faster than real time for a typical simulation application using a time step size of 0.1 s.