Field Observation of Orbital Motion in Waves

在本研究计画中，利用波浪中轨道运动的资料，探讨两个主要的目标，一个是波浪方向函数的特性，另一个是波浪力系数的性质。主要结论如下：利用海洋研究平台上悬挂的波高仪阵和三分量海流计对海浪进行了观测。用最大似然法确定了实测波浪的方向谱。比较了这两套仪器得到的结果，研究表明：（a）由于Mitsuyasu等人，本文所建立的模型是在海洋中部波浪资料充分发展的基础上发展起来的，它与本文所建立的模型具有很好的一致性，并且包含了广泛的发展阶段。(b)风速、波高和传播参数Smax的时间序列， 关于我们 ak频率之间有较好的相关性，Smax值可由波高的有效值实际估算。(c)波高计阵列和三分量海流计测得的波能角扩展特性的测量值显示出良好的一致性。波浪力是用两个安装在试验圆柱两端的二分量测力计测量的。发现以下内容。(d)由随机波浪记录的完整力时间序列的最小二乘拟合获得的Cp和CH值作为由有效轨道位移和圆柱直径定义的Keulegan-Carpenter数K2的函数是有序的，但是由逐波最小二乘拟合确定的Cp和CH值是广泛分散的。(e)Morison公式较好地反映了作用在圆柱上的波浪力，其预测值与实测值之比为90%，且在整个试验过程中非常稳定。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