大型气浮沉箱拖航过程中的垂荡运动特性分析

Research on the heave motion characteristics of a towed large air floating caisson

为防止大型气浮沉箱在浅水海域拖航中由于垂荡值过大造成触底,本文研究了气浮沉箱的垂荡运动特性。采用MOSES分析软件获得气浮沉箱在不规则波波浪下垂荡位移的响应,经Welch法分析得到气浮沉箱的固有垂荡周期;利用周期不同的规则波浪进行气浮沉箱拖航模拟,以此获得相应的垂荡运动位移幅值最大点对应的周期值范围。同时,分析了理论垂荡固有周期值的计算过程,并研究了不同吃水对气浮沉箱垂荡运动特性的影响。证明经过MOSES分析软件和功率谱估计得到的垂荡固有周期值是合理的,可以参与水动力学计算并作为选取附加质量因素时的参考值;随着吃水的加大或分舱内气压的减小,垂荡固有周期值有增大的趋势。

To prevent contact between the seabed and a large air floating caisson in shallow waters due to large heave when towing, the heave motion characteristics of the caisson are studied in this paper. The analytic software MOSES was used to obtain the vertical displacement of the caisson due to irregular waves. Then, fast Fourier trans-form of this displacement and the Welch algorithm were used to acquire the natural heave period of the caisson. To obtain the range of the cycle corresponding to the maximum displacement amplitude point of the heave motion, reg-ular waves of different periods were used to simulate the towing process of the caisson. Moreover, the calculation process of the theoretical natural heave period was analyzed, and the influence on the heave motion of the caisson with different drafts was studied. It is proven that the natural heave period can be reasonably obtained using MOSES and a power spectrum estimation method. The natural heave period can be used in the hydrodynamic calculation andas the standard value when selecting the additional mass factor. With an increase in the draft or a decrease in the cabin pressure, the natural heave period shows an increasing trend.