Prediction of Hydroelastic Behavior of a Very Large Floating Structure in Waves and Current

为建立超大型浮式结构物在波浪和水流中(或等效在波浪中以前进速度前进)的水弹性行为的预报方法，进行了理论和试验研究。1.建立了超大型浮体在波浪和水流中的水弹性响应的边界积分方程法，在低流速假设下采用势流理论。这允许速度势在前进速度的扰动序列中展开。保留前进速度中的先导阶项，将边值问题化为两组仅含零速格林函数的积分方程组。在零速情况下，采用边界元技术可以有效地求解。应用该理论对波浪中以前进速度前进的圆板的水弹性行为进行了预测。结果表明，小航速对板的水弹性响应有显著影响。其对弯曲应变的影响比对位移的影响更显著。仅考虑多普勒效应的近似预测低估了前进速度的影响。为了验证理论方法的有效性，利用一个超大型浮式结构物在波浪(无流)中的小比例模型进行了波浪水槽试验。理论计算与实验结果吻合较好，从而证实了理论预测的正确性。

Theoretical and experimental investigations have been performed with the purpose of establishing a method of prediction for the hydroelastic behavior of a very large floating structure in waves and current (or equivalently advancing with forward speed in waves). The results of the research are summarized as follows :1. A boundary integral equation method was developed to predict the hydroelastic response of a very large floating structure in waves and current A potential flow theory is employed with low current speed assumption. This permits the velocity potential be expanded in a perturbation series of forward speed. Retaining the leading-order terms in the forward speed, the boundary-value problem is reduced to two sets of integral equations which only contain the zero speed Green's function. The solution can be obtained efficiently by applying the boundary element technique which is well-developed for zero speed case.2. The theory was applied to predict the hydroelastic behavior of a circular plate advancing with forward speed in waves. It was shown that the hydroelastic response of the plate is significantly influenced by the presence of small forward speed. Its effect is more significant for the bending strain than the displacement. The approximate prediction taking only account of Doppler's effect is found to underestimate the forward speed effect.3. In order to validate the theoretical approach wave tank tests have been performed using a small scale model of a very large floating structure in waves (without current). Agreement was found to be satisfactory between theory and experiment, thus confirming the validity of the theoretical prediction.