Estimation of Directional Wave Spectrum of Encounter Waves on Board, by an Array of Two Wave-height Meters

在本研究项目中，作者试图开发一种简单的方法来估计船舶的方向波谱。1987年，他们首先设计了一个由两个波高仪组成的阵列，并在波浪水池中进行了测试。然后，他们通过在一艘蒸汽船船头两侧安装传感器的阵列获得了在Nojima-Zaki附近遭遇的波高记录。利用双通道快速傅立叶变换得到了相遇波谱以及两波相干性和相位差随频率的变化关系。他们在个人计算机上开发了一个程序，利用从FFT分析仪传来的这些数据来估计实际海浪谱和方向波谱。在传统的固定位置估计中，需要三个以上的传感器，配置成星形或三角形。虽然他们证明了在本研究项目的方法中，通过添加船舶速度矢量的阵列来估计两系列相遇波记录是可能的，但在1988年，他们改进了实时显示方向波谱的程序。然而，这还没有在船上得到验证，因为传感器在前往真正的海洋实验的途中被卷走了。因此，他们尝试了另一种方法来估计海浪的方向。他们用微波多普勒雷达测量了相对波速，该雷达用于他们的波高计，并沿方位旋转辐射角。在波浪水槽和真实海面上的试验表明，该方法对海浪方向谱的估计是可行的，但仍有一些问题有待解决。目前，波浪仪阵列实时显示的实验已基本准备就绪，不久将进行。

The authors tried to develop a simple method to estimate directional wave spectra from a steaming ship, in the present research project.At first in 1987, they designed an array comprised of two wave height meters and tested it in a wave tank. Then they acquired the encounter wave height records off Nojima-zaki by the array whose sensors were installed at the both sides of the bow of a steaming ship. The encounter wave spectra and the frequency dependency of coherency and phase difference between the two wave records are deduced by a 2-channel FFT analyzer. They developed a program on a personal computer to estimate the real wave spectrum and directional wave spectrum using these data which were transmitted from the FFT analyzer.In the conventional estimation at a fixed position, more than three sensors are necessary, allocated with star- or delta-shape. While they proved that estimation was possible from the two series of encounter wave records by the array with an additional information of a velocity vector of a steaming ship, in the method of the present research project.In 1988, they improved the program for the real-time display of the directional wave spectrum. It has not been verified yet on board, however, because the sensors were swept away on the way to the real ocean experiment.Thus they tried another method to estimate the wave direction. They measured the relative wave velocity by a microwave Doppler radar, used in their wave height meter, with rotating the radiation angle azimuthally. Some tests in a wave tank and real sea show the applicability of this method to the estimation of the directional wave spectrum, although there are some problems to be solved.The experiment of real-time display by the wave meter array is almost prepared now and will be executed in near future.