Safety of dynamic stability in waves of domestic coastal sea-going ships

In this work, the safety risk of dynamic stability of domestic coastal sea-going ships in waves has been studied by evaluating parametric roll, pure loss of stability and synchronous roll, based on the newly developed second generation intact stability criteria. The Froude-Krylov assumption and free trim method are used to calculate the righting levers and stability characteristics in waves, simplified nonlinear motion equation and frequency domain motion equation based on hydrodynamics are used to obtain the time/ frequency domain results of roll amplitude and acceleration of parametric and synchronous roll, and the stability characteristics are used to evaluate pure loss of stability. Finally the risk probabilities of three failure modes are obtained based on the sea-states probability. The study shows that the typical ship types may be vulnerable to pure loss of stability and synchronous roll, and assessment results of dynamic stability safety level in waves are generally consistent with the accident and investigation results. There is a risk of dynamic stability accidents in waves for typical Chinese coastal sea-going ship types. It is suggested that in the optimization of ship design, ship operation and sailing under adverse sea conditions, maritime supervision and accident investigation, special attention should be paid to the above safety level and accident risk assessment results.