海浪绘制中波浪谱的选择和参数计算

On Selection and Parameter Calculation of Wave Spectra in Ocean Wave Rendering

分析了Phillips波浪谱结构,指出该谱是由符合Neumann形式的频率谱和国际拖曳水池会议推荐的方向分布函数构成的方向谱,Phillips谱的频率谱与P-M谱接近。参考P-M谱提供的方法给出了Phillips谱风速的确切含义并计算出该谱的常数,解决了其在应用中未尽的问题。比较PM-ITTC方向谱和Phillips谱的绘制结果,发现用Phil-lips谱绘制的海浪低频长波更加突出。对Phillips谱和PM-ITTC方向谱进行比对,发现Phillips谱的谱峰频率与PM-ITTC方向谱接近,但谱宽更窄,能量更集中于低频部分。为Phillips谱增加了风距参数,使绘制结果能反映风速、风距对海浪的影响。绘制的海浪传播方向、波高随风速变化而变化,与航海实际情况相符,已应用于航海模拟器。

The structure of Phillips wave spectra was analyzed. Phillips spectra is directional spectra,and can be separa- ted into the frequeney spectra and directional spreading function. Its frequency spectra accords with the Neumann spec- tra form,and is familiar with P-M spectra. Its directional spreading function is the function recommended by Interna- tional Towing Tank Conferenee. By referencing P-M spectra, the wind speed of Phillips spectra is specified and its con- stant is calculated,which solves the unsettled problems in application. By comparing the rendering results of PM-IT-FC direetional spectra and Phillips spectra, it is found that long waves with low frequency band are more obvious in ocean wave rendered with Phillips spectra. Additionally, the study shows the peak spectral frequency of Phillips spectra is close to that of PM-ITTC directional spectra, but its spectral width is smaller and its wave energy more concentrates in low frequency band. Fetch length is added as a parameter of Phillips spectra. So the rendering result can reflect the in- fluence of both wind speed and fetch length on rendered ocean wave. The propagation direction and wave height of the rendered ocean wave vary as wind speed changes, which conforms to the actual condition in navigation. The method is used in navigation simulator.