Field Observation of Orbital Motion in Waves

在本研究项目中，利用波浪中的轨道运动数据对两个主要指标进行了研究，一个是波向函数的特性，另一个是波浪力系数的性质。得到的主要结论如下：利用海洋研究平台上悬挂的波高仪阵列和三分量流速仪对海浪进行了观测。用最大似然法确定了实测海浪的方向谱。对这两套仪器的结果进行了比较，研究发现：(A)三谷等人在大洋中段充分发展的波浪数据基础上发展起来的方向函数的表示，与本文根据海岸附近收集的波浪数据确定的方向函数的表示很好地一致，并包含了广泛的发展阶段。(B)PE…的风速、波高的显著值和扩展参数Smax的时间序列较多的AK频率有较好的相互关系，Smax的值可以从波高的显著值来估算。(C)用波高计阵列和三分量流速仪测得的波能角传播特性的实测值具有很好的一致性。(D)由随机波浪记录的完整力时间序列的最小二乘拟合得到的Cp和Ch值是由显著轨道位移定义的Keulegan-Carpenter数K2和圆柱体直径的函数，但通过逐波拟合的最小二乘法确定的值具有广泛的分散性。(E)作用在圆柱体上的海浪力可以用Morison公式很好地描述；用该公式预测的波浪力与直接测量的波浪力的比率为90%，并且该比率在整个实验过程中非常稳定。较少

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