随机横浪中船舶倾覆过程模拟与安全域计算

The Simulation of Capsizing Route and the Calculation of Safe Basin of the Ship in the Stochastic Beam Seas

研讨了随机海浪中船舶非线性随机横摇运动倾覆过程和安全域问题。考虑非线性阻尼、非线性复原力矩和随机波浪,建立了随机横浪中船舶运动的随机非线性微分方程。考虑两参数海浪谱和不同的有义波高,计算随机波浪力矩,采用简谐加速度数值计算方法求解随机微分方程,进行了随机倾覆过程的数值模拟。考虑船舶运动的瞬时状态,发展了胞映射方法计算随机非线性横摇运动安全域的方法,并编制了计算机程序。模拟了一条渔船不同有义波高作用下横摇倾覆过程,考虑不同的初始条件及随机波浪参数,在初始值平面上采用胞映射法构造了渔船航行的安全域。波高较小时,安全域是一个连续的区域;随着有义波高增大,安全域面积减小并且不再连续,倾覆域和安全域相互包围。计算结果表明,船舶运动的瞬时状态对安全域具有重要影响,而且随机海浪中安全域具有随机特性。

The safe basin and capsizing route of nonlinear random motion of the ship in the high seas are investigated in this paper. The random nonlinear differential equation of ship＇s motion is established considering the nonlinear damping, nonlinear recover moment and random waves. The stochastic wave moments are calculated considering two coefficient seas spectra and different significant wave heights. And the random capsizing route is numerically simulated by solving the stochastic differential equation by means of harmonic acceleration method （HAM）. Thereafter, the process of calculating the safe basin of ships＇ random motion with cell mapping method is developed and the computer program is worked out considering the instantaneous states and random waves. The capsizing route of a fishing vessel is simulated for different significant wave heights. A safe basin in the initial value plane is constructed with cell mapping method for the different initial conditions and random wave parameters. When the significant wave height is smaller, the safe basin is a continuous area. As the significant wave height rises, the area of the safe basin reduces and is no longer continuous, and the safe area and the capsizing area are interlaced. It is shown that the influence of the instantaneous states of ship motion on the safe basin is important and the stochastic behavior of safe basin is found in the calculations.