A new scheme of nonlinear energy transfer among wind waves: RIAM method-algorithm and performance-
A new scheme of nonlinear energy transfer among wind waves: RIAM method-algorithm and performance-
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风浪间非线性能量传递新方案：RIAM方法-算法与性能-
DOI：
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发表时间：
1996
期刊：
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通讯作者：
A. Masuda
中科院分区：
文献类型：
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作者：
K. Komatsu;A. Masuda
在增田（Masuda）的严谨方法基础上，开发了一种用于计算风浪之间非线性能量传递的数值格式（RIAM方法）。然后，通过将其应用于各种形式的风浪谱以及不同的风浪演变情况，并主要与WAM方法进行比较，检验了RIAM方法的性能。RIAM方法将增田方法的计算时间缩短了300倍，但它仍然比WAM方法慢2000倍，这仅仅是因为RIAM方法要处理数千种共振配置，而WAM方法仅处理一种。事实证明，即使对于窄带宽谱或双峰谱，RIAM方法也能给出准确的结果，而WAM方法经常会计算出不切实际的非线性能量传递函数的大小和模式。在风浪谱的有限时长演变过程中，RIAM方法在谱峰的低频侧产生单峰方向分布，而WAM方法在那里产生虚假的双峰分布。然而，在较高频率下，两种方法都给出具有两个倾斜最大值的双峰方向分布。与WAM方法相比，RIAM方法促进了风浪总能量和峰值周期的增长。尽管如此，在两种方法中，户田（Toba）的3/2次幂定律常数几乎都接近相同的标准值0.06。对于窄带宽谱或受到小凸起或凹陷扰动的谱，RIAM方法往往会恢复谱的单调平滑形式，而WAM方法经常会产生不切实际的凸起或凹陷。
A numerical scheme for calculating the nonlinear energy transfer among wind waves (RIAM method) was developed on the basis of the rigorous method of Masuda. Then the performance of the RIAM method was examined by applying it to various forms of wind-wave spectra and different situations of wind-wave evolution, in comparison mainly with the WAM method. The computational time of the Masuda method was reduced by a factor of 300 by the RIAM method, which is still 2000 times slower than the WAM method simply because the RIAM method processes thousands of resonance configurations whereas the WAM method does only one. The RIAM method proves to give accurate results even for spectra of narrow band widths or bimodal spectra, whereas the WAM method often calculates an unrealistic magnitude and pattern of nonlinear energy transfer functions. In the duration-limited evolution of wind-wave spectra, the RIAM method yields a unimodal directional distribution on the low-frequency side of the spectral peak, whereas the WAM method produces a spurious bimodal one there. At higher frequencies, however, both methods give a bimodal directional distribution with two oblique maxima. The RIAM method enhances the growth of the total energy and peak period of wind waves in comparison with the WAM method. Nevertheless, Toba's constant of his 3/2-power law approaches almost the same standard value of 0.06 in both methods. For spectra of a narrow band width or for those perturbed by a small hump or depression, the RIAM method tends to recover the monotonic smoother form of spectrum whereas the WAM method often yields unrealistic humps or depressions.
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