随浪中纯稳性丧失直接评估方法研究

Study on numerical approach on pure loss of stability in following waves

针对国际海事组织(IMO)正在制定的船舶第二代完整稳性衡准中的纯稳性丧失直接评估衡准,文章构建了纵荡-横摇2自由度运动耦合的数学模型,进行了随浪中纯稳性丧失直接评估。该方法首先在纵荡方程中考虑了随航速变化螺旋桨推力和静水阻力,及随瞬时船—波相对位置变化的时域纵荡波浪力。其次在横摇方程中基于Froude假设采用静平衡法求解随瞬时船—波相对位置和横倾角变化的时域复原力变化,同时考虑了初始横倾、非线性横摇阻尼和横倾水动力导数的影响,构建了纵荡—横摇2自由度耦合运动方程。最后采用ONR内倾船开展了随浪规则波中纯稳性丧失试验,验证了文中提出纵荡-横摇2自由度运动耦合的数学模型的可靠性,并进一步分析了初始横倾角、纵荡和横倾水动力导数对纯稳性丧失的影响,为纯稳性丧失直接稳性评估衡准的应用奠定了基础。

The guidelines for direct stability assessment of pure loss of stability are currently under development at the International Maritime Organization(IMO)for the second generation intact stability criteria.A surge-roll coupled equation named as 2 DOF is established for predicting pure loss of stability in following waves.Firstly,the thrust and the resistance of calm water are varied with speed and the wave force is varied with the relative position between ship and wave in the surge motion.Secondly,the restoring variation is calculated by a static blance method based on Froude assumption,and the relative position between ship and wave and the heeling angle are taken into account.Thirdly,the initial heeling angle,the nonlinear roll damping and the heel-induced hydrodynamic forces for large heel angle in calm water are considered in the 2 DOF mathmatical model.Finaly,model tests are carried out for pure loss of stability in following waves,and the effect of the initial heeling angle,the surge motion and the heel-induced hydrodynamic forces on pure loss of stability are studied for direct assessment of pure loss of stability.