Field Observation of Orbital Motion in Waves

本课题利用波中的轨道运动数据，研究了波的方向函数特征和波力系数的性质两个主要目标。主要结论如下：用悬挂在海洋研究平台上的波高计阵列和三分量流计对海浪进行了观测。用最大似然法确定被测波的方向谱。用这两套仪器得到的结果进行了比较，调查显示：(a) Mitsuyasu等人根据海中较发达的波浪资料得出的方向函数表示与本文从海岸附近收集的波浪资料得出的方向函数表示吻合较好，并且包含了较宽的发育阶段。(b)风速、波高显著值和传播参数Smax的时间序列，二者之间的相互关系较好，从波高显著值可以实际估计出Smax的值。(c)波高计阵列与三分量流计测得的波能角传播特性实测值吻合较好。波浪力是用设置在测试筒两端的两个双分量测力计测量的。发现了以下内容。(d)随机波记录的完整力时间序列的最小二乘拟合得到的Cp值和CH值作为由显著轨道位移和圆柱体直径定义的Keulegan-Carpenter数K2的函数具有良好的有序性，但由逐波最小二乘拟合确定的Cp和CH值具有广泛的离散性。(e)莫里森公式能很好地表示作用在圆柱上的海浪力；该公式预测的波浪力与直接测量的波浪力之比为90%，并且在整个实验过程中该比例非常稳定。少

In this research project, two major target were investigated using the data on the orbital motion in waves, one was the characteristics of wave directional function and another was the nature of the wave force coefficient. The main conclusions obtained are as follows ;Ocean waves have been observed with a wave height meter array and a three component current meter suspended from an ocean research platform. Directional spectra of measured waves are determined using the Maximum Likelyhood Method. The results obtained with these two sets of instruments were compared and investigations revealed the following ;(a) representation of directional function due to Mitsuyasu et al., which was developed on the basis of the well developed wave data in mid-ocean, are in good agreement with that determined here form wave data collected near the coast and contained wide range of the development stage.(b) time series of wind speed, significant value of wave height and spreading parameter Smax at the pe … More ak frequency were in good mutual relation, and the value of Smax may be estimated practically from the significant value of wave height.(c) measured values of the characteristics regarding the angular spreading of wave energy obtained with the wave height meter array and three-component current meter showed good agreement.The wave forces were measured with two 2-component dynamometers set at either end of the test cylinder. The following was found.(d) the values of Cp and CH obtained from least squares fit of the complete force time series of a random wave record were well ordered as a function of Keulegan-Carpenter number K2 defined by significant orbital displacement and the diameter of the cylinder, but those determined by the least squares fit on a wave-by-wave basis were widely scattered.(e) ocean wave force exerted on the cylinder was well represented by Morison's formula ; the ratio of predicted wave force by this formula to the directly measured force was 90%, and the ratio was very stable throughout the experiments. Less