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蒸汽船舶的定向波谱。1987年，他们首先设计了一个由两个波高计组成的阵列，并在波浪槽中进行了测试。然后，他们通过安装在一艘蒸汽船船头两侧的传感器阵列获得了野岛崎附近的遇浪高度记录。利用2通道FFT分析仪，推导了两波记录的相遇波谱以及相干和相位差的频率依赖关系。他们在个人电脑上开发了一个程序，利用这些从FFT分析仪传输的数据来估计真实的波谱和定向波谱。在传统的固定位置估计中，需要三个以上的传感器，以星形或三角形分配。而在本研究项目的方法中，他们证明了阵列在附加船舶速度矢量信息的情况下，可以从两个系列的遇波记录中进行估计。1988年，他们改进了实时显示定向波谱的程序。然而，这还没有在船上得到证实，因为传感器在前往真正的海洋实验的途中被冲走了。因此，他们尝试了另一种方法来估计波的方向。他们用微波多普勒雷达测量了相对波速，这种雷达用在他们的波高仪上，并沿方位角旋转辐射角。在波浪槽和实际海中进行的试验表明，该方法对定向波谱的估计是适用的，但仍存在一些有待解决的问题。目前，利用波计阵列进行实时显示的实验已基本完成，并将在不久的将来进行。

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.