PREDICTION METHOD FOR NON-GAUSSIAN BEHAVIOR AND ITS EXTREMUM OF A MOORED FLOATING BODY IN NON-GAUSSIAN MULTI-DIRECTIONAL IRREGULAR OCEAN WAVES

恶劣海况下的运动响应或波浪载荷的极值预报方法尚未发展起来，因为响应是非高斯的。有许多海洋设施或散货船遭受结构破坏，沉没，失去了许多人的生命。已有的几个例子表明瑞利方法不适用于非高斯情况。这就是为什么我们开始发展实用的非高斯过程极值预报方法。我们首先尝试预报悬链式系泊浮式结构物在多向波浪中的低频运动极值。如果只有外部波激励是非线性的，其他项、辐射水动力、阻尼项和恢复项都是线性的，则Naess或Kato-Kinoshita发展的方法很好，但如果在运动方程的左侧引入非线性项，则基于Naess或Kato-Kinoshta的分析方法不起作用。在此基础上，提出了适用于基于仿真设计的全非线性、非高斯型过程的唯一实用预报方法--时域仿真方法，并在此基础上开发了先进航速多向波浪中船舶运动、波浪载荷和船体非定常压力的时域仿真程序。此外，我们还将非线性项引入到该时间域模拟中。

The prediction method of extremum for motion responses or waves loads in severe sea conditions have not been developed yet, since the responses are non-Gaussian. And there have been many marine facilities or bulk-carriers which suffered structural damages, sank and lost many lives. There have reported several examples which shows that the Rayleigh method was not hold for non-Gaussian cases. That is the reason why wer start to develop the practical prediction method of extremum for non-Gaussian process.We first tried to predict extremum of low frequency motions of a catenary moored floating structures in multi-directional waves. If only external wave excitations are non-linear and the other terms, radiation hydrodynamic forces and damping term and restoring term are all linear, then the method developed by Naess or Kato-Kinoshita works well, however, if we introduce non-linear terms in the left hand side of the equation of motion, the analytical method based on Naess or Kato-Kinoshta does not function. Then we conclude that the only practical prediction method for full non-linear, non-Gaussian process is the time domain simulation method which is applicable to so called simulation based design.We then developed the time domain simulation code for ship motions, waves loads and unsteady pressures on a ship hull with advanced speed and in multi-directional waves. Moreover we introduce non-linear terms to this time domain simulation.