规则波六自由度回转运动预报

Simulation of 6-DOF Turning Motions in Regular Waves

基于经典MMG分离式模型,考虑三自由度船舶平面运动与横摇、纵摇及垂荡运动的耦合,提出波浪中船舶六自由度操纵—耐波全运动模态的数学模型。采用经验公式估算船体力、桨力及舵力。在波浪力建模中,采用三维面元法计算不同浪向下六自由度一阶频域波浪力及二阶波浪漂移力,并利用卡明斯脉冲响应,在计入时间效应的前提下,将频域的阻尼系数和绕射波力分别转化为时域内的辐射与绕射波力。应用该模型对S175集装箱船在规则波中的回转运动进行数值模拟,通过与自航模试验结果进行对比,验证了模型的准确性,模拟结果误差在10%以内。最后,应用该模型分别就回转轨迹和回转横摇运动讨论了操纵—耐波耦合作用的影响。结果表明:在低频波浪下,回转横摇对回转轨迹的影响效果为5%;在高频波浪下,回转轨迹对回转横摇运动的影响效果为20%。

A 6-DOF mathematical model which combines the traditional 3-DOF MMG （ship manoeuvr-ing mathematical model group） model and seakeeping motions of roll, pitch, and heave is presented in this paper to simulate the ship maneuvering motions when coupled with seakeeping motions in waves. Hydrody-namic derivatives and propeller and rudder forces are estimated with empirical formulas using basic ship parameters. As for wave forces, the first order ones are evaluated in time-domain by using Cummins im-pulse response function; the second order ones are obtained by taking its mean average part into account solely. Furthermore, the 6-DOF model is employed to simulate the maneuvering and seakeeping motions of a container ship （S175） simultaneously. A code of this model is correspondingly developed, which is then tested against the measured data obtained from seakeeping experiments and free running model tests. The simulating error is seen to be within 10%. Finally, the coupling effects between ship maneuvering and sea-keeping motions are studied by comparing the turning trajectories and roll motions in different conditions. The results show that the turning roll motion makes the turning trajectory 5% stronger in low frequencies, while the turning drift makes the turning roll motion 20%stronger in high frequencies.