Calculation of ship roll hydrodynamic coefficients in regular beam waves

Simulation of a ship’s roll motion through equation-based approaches requires restoring moment, added mass moment of inertia and damping coefficients. Accurate estimation of these coefficients enhances the prediction of ship roll response at a resonance condition. However, the magnitude of these coefficients in regular beam seas and close to a resonance condition is unknown. The present study adopts numerical and experimental simulations to investigate the effects of different wave heights and wave frequencies on ship motion characteristics. The motion characteristics results from numerical simulations are compared against experimental measurements, and a good correlation is achieved. The restoring moment in dynamic conditions is calculated and compared to the hydrostatic restoring moment. The dynamic restoring moment is greater than the hydrostatic restoring moment for some wave frequencies and smaller for other wave frequencies. The magnitudes of roll damping and added mass moment of inertia coefficients are calculated at different wave heights and frequencies, and the results yield that there is quite a nonlinear relationship between the roll hydrodynamic coefficients and roll motion characteristics.