A Study on the Effect of Parametric Rolling on Heave and Pitch Motions in Head Seas
A Study on the Effect of Parametric Rolling on Heave and Pitch Motions in Head Seas
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发表时间：
2013
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通讯作者：
Jiang Lu;M. Gu;N. Umeda
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作者：
Jiang Lu;M. Gu;N. Umeda
国际海事组织(海事组织)目前正在制定第二代完整稳定性标准中用于直接评估参数滚转稳定性的方法。为了给参数横摇预报提供可靠的数值方法，通过模拟和试验研究了参数横摇对规则头海垂荡和纵摇运动的影响。首先，采用基于非线性条带理论的垂荡-横摇-纵摇耦合数学模型，计算了考虑参数横摇的规则头海中的垂荡和纵摇运动。其次，在光学跟踪器用于测量船舶运动的情况下，通过模型实验研究了参数横摇对垂荡和纵摇运动的影响。最后，利用傅立叶变换对横摇和纵摇运动进行了频域分析。实验和仿真结果都表明，参数滚转对横摇和纵摇运动有明显的影响，并且新观察到一个明显的现象，即参数滚转发生时，实验中的横摇运动中含有亚谐分量。然而，这种明显的现象在数值模拟中不能清晰地再现，因此参数滚转对垂荡和纵摇运动的影响有待于在参数滚转直接稳定性评估的数值方法中进一步研究。
The methods to be used for direct stability assessment of parametric rolling are now under development by the International Maritime Organization (IMO) in the second generation intact stability criteria. In order to provide a reliable numerical method for predicting parametric rolling, the effects of parametric rolling on heave and pitch motions in regular head seas are investigated by simulations and experiments. Firstly, a coupled heave-roll-pitch mathematical model based on a nonlinear strip theory is used to calculate heave and pitch motions in regular head seas with parametric rolling taken into account. Secondly, model experiments are conducted to investigate the effect of parametric rolling on heave and pitch motions where an optical tracker is used to measure ship motions. Finally, time-domain heave and pitch motions are analyzed in the frequency-domain by the Fourier transformation. The both results of experiments and simulations show that heave and pitch motions are obviously affected by parametric rolling and one distinct phenomenon is newly observed that the pitch motions in experiment include subharmonic component when parametric rolling occurs. However the distinct phenomenon does not clearly reproduced in numerical simulation, therefore the effects of parametric rolling on heave and pitch motions should be further investigated in the numerical method for direct stability assessment of parametric rolling.