三体船在斜浪规则波中运动响应预报方法研究

Prediction of ship motions of trimaran in oblique regular wave

对于三体船在波浪中的水动力预报,航速效应和主体与片体间水动力干扰效应是水动力载荷合理预报的关键之处,需合理考虑。二维半势流理论可较为准确反映上述效应,已在三体船顶浪中垂向运动响应理论预报上获得了较为满意的结果。在此基础上,该文探讨了该方法在三体船斜浪中运动特别是横摇预报上的应用。为较准确获得三体船横摇运动时粘性阻尼贡献,采用三体船模静水中自由横摇衰减试验获得了自由横摇运动衰减曲线,并经能量法处理获得了船舶横摇阻尼系数。然后,结合二维半理论,获得了三体船运动数值解。数值解与斜浪规则波中运动响应模型试验结果符合较好,反映本文所采用的数值方法可较好地预测三体船斜浪中水动力载荷和运动,可用于三体船在波浪中耐波性评估。

It＇s crucial to include the forward speed effect and the hydrodynamic interference effect between the main hull and demi-hulls for rational prediction of hydrodynamic forces of trimaran in waves. The 2.5D potential flow theory can properly embody these effects and has already got satisfactory prediction for wave induced heaving motions of trimaran in head seas.Using the previous developed numerical code based on 2.5 D theory, the application of the method to predict the wave induced ship motions especially roll motion in oblique waves is investigated and presented in this paper. In order to obtain the roll damping of trimaran with a good accuracy, the free decay rolling experiment has been performed and the energy method is used to get the rolling damping coefficient from the measured rolling angel time series. Combining the obtained rolling damping coefficient, the 2.5 D theory is applied numerically to predict the rolling motion of trimaran in waves. The numerical results agree quite well with the experimental data of ship motions in regular oblique waves which shows that the numerical method applied in this paper can give a good estimation of hydrodynamic loads and the motions of trimaran in oblique wave and be used to predict the seakeeping performance of trimaran.