Capsizing Probability Prediction for a Large Passenger Ship in Irregular Beam Wind and Waves: Comparison of Analytical and Numerical Methods

Abstract

This paper presents a comparison of capsizing probability of a large passenger ship using an analytical method and a numerical experiment in beam wind and waves. The analytical method uses Belenky's piece-wise linear approach, and the numerical experiment is based on the Monte Carlo method to realize both fluctuating wind and irregular waves with random phases. The effect of the gustiness is modeled by the Davenport spectrum. The result of the numerical experiment is verified by a two-sided statistical test with a confidence level of 0.05. Outcomes of both methods are compared for various sea states covering extremely severe sea states, severe sea states, and moderate sea states. As a result, it was pointed out that quality of predicted capsizing probability using numerical experiment increases when the number of realizations increase. Poisson process assumption in the analytical method seems to be a breakdown in extremely severe sea states, but it may be applicable in severe sea states, which the current weather criterion assumes. Numerical experiment for capsizing probability could be impractical in moderate sea states.