Improved maneuvering-based mathematical model for free-running ship motions in following waves using high-fidelity CFD results and system-identification technique

Abstract

Predicting maneuverability and stability of a free running ship in following and quartering waves are one of the most important topics to prevent broaching; however current mathematical models show quantitative errors with the experimental data while high-fidelity CFD simulations show quantitative agreement, which provides the opportunity to improve the mathematical models for free running ship dynamics in waves. In this study, both maneuvering coefficients and wave model in the mathematical model are improved utilizing system identification technique and CFD free running outputs. From turning circle and zigzag calm water CFD free running data, the maneuvering coefficients are estimated. The wave correction parameters are introduced to improve the wave model, which are found from a few forced and free running CFD simulations in waves. The mathematical model with the improved parameters shows much better agreement with experiments in both calm water and waves than the original mathematical model. The original mathematical model was based on the maneuvering coefficients estimated from several captive tests and wave forces calculated from linear Froude-Krylov forces and diffraction forces based on a slender ship theory.