Undesirable Ship Capsizal in Regular Beam Sea

Since the classical linear dynamics of ship motion can not explain some undesirable ship capsizal, the nonlinear dynamic theory was adopted to study the anti capsize capacity of ship. By using the approximate method, the solution to the nonlinear differential equation which governs the ship motion in regular beam sea is attained. The stability of this solution is analyzed based on the bifurcation method and Floquet theory. The result shows that the ship motion will become chaos after the double period bifurcation and lead to capsizal. The stability loss of ship motion is also one of the approaches resulting in the ship's capsizal. Therefore, double period bifurcation is defined as a capasizal mechanism. The biased angle is originally selected as a sensitive factor to study its effects on the ship's anti capsizal capacity. The research shows that biased angle will seriously damage the ship's stability, so that it is very important to control the biased angle for ship's safety.