AN ADDITION FOR ROLL MOTION COMPUTATION INTO YTU DEEP SHIP MOTION CODE

The primary purpose of this study is to investigate the damping characteristics of the ship’s roll motion. The second goal is to explore the damping effects on the solution of roll motion, considering the ship’s forward speed, wave frequency, and initial roll amplitude. Roll motion is a more critical yet less understood response compared to other degrees of freedom due to the complexity arising from viscosity. Roll damping comprises several components, which are divided into five categories with the assistance of empirical formulas created as a result of experiments. Wave damping is calculated by linear diffraction/radiation theory so it is a linear damping. Lift damping is also considered linear. However, eddy making, skin friction, and bilge keel damping are not linear due to dependency on the initial roll amplitude. The effects of roll amplitude, the ship’s forward speed, and wave frequency are investigated in this paper with the empirical formulas developed by Ikeda and Himeno. Frequency domain analyses of the roll motion are also conducted for the selected cases to demonstrate the credibility of the proposed paper. All codings are performed by using MATLAB and it will be embedded in YTU DEEP Ship Motion Program.