Evaluation of Dynamic Stability Safety for Damaged Ships under Wind and Waves

For assessment of the dynamic stability of damaged ship under actions of wind and waves, existing methods quantify the impact of waves on ship stability via the resonance angle, which presents certain limitations when evaluating the survivability and anti-sinking capability of damaged ships in real environments. In this work, a novel method is proposed to evaluate the dynamic stability of damaged ship in waves, based on the extreme value analysis of the roll motion responses. Firstly, the static stability of the DTMB-5415 under typical damage conditions is evaluated. Secondly, a single-degree-of-freedom roll motion equation for a damaged ship under the combined action of wind and waves is constructed, in which the roll damping coefficient is obtained using the CFD method. Then the roll motion response of the damaged ship is calculated by using the numerical method. Finally, the Monte Carlo method and the Gumbel method are applied to predict the extreme roll motion response for the damaged ship under varying wind and wave conditions, the dynamic stability safety of the ship is evaluated and compared with the results obtained through the dynamical upsetting angle. It is found that the influence of the wave parameter such as significant wave height and wave period on the dynamic stability of the damaged vessel can be considered in the proposed method. Therefore, it provides a more comprehensive consideration for the dynamic stability than the traditional method based on the dynamical upsetting angle, offering an important reference for evaluating the stability of damaged ships.