Researches on the motion and flooding process of a damaged passenger ship in regular and irregular beam waves

The motion and flooding process of a damaged passenger ship in regular and irregular beam waves are investigated experimentally and numerically at zero forward speed. Experiments are carried out on the intact and damaged ship models with varied wave periods and different wave steepness in regular and irregular waves. The water height inside the damaged compartments and ship's roll are measured and compared to the numerical results from the potential flow method with a flooding model based on the modified Bernoulli's equation. Experiments are conducted to verify numerical method's capability of predicting ship's motion under unsteady condition in the irregular wave. The results indicate that the potential flow method can accurately estimate ship roll and internal water height, but it fails to capture the multi-frequency characteristic of wave height variation in large-wave-steepness cases. The flooding into the side damaged opening increased the period of ship's roll and the roll amplitude increased with increasing wave steepness in both ship states. The roll amplitude of the damaged ship is smaller than that of an intact one under same condition in both regular and irregular wave, although the maximum rolling angle can exceed the latter under certain conditions. More nonlinear effects throughout the flooding process, as well as unsteady effects in irregular waves, should be added to improve the accuracy of the numerical method.