海浪外观统计与内部结构关系的数值研究

基于数值模拟的三维随机海面,从时间域和空间域两个角度对海浪的外观特征和内部结构间的关系进行了研究,得出了一些在工程应用上有参考价值的结果.文章认为,将波面看作是若干随机正弦波叠加的海浪结构模型,用于描述平稳、均匀和窄谱的海况时,其频谱分析结果与外观统计结果基本上是一致的;但是,当海面处于谱宽度较大的风浪或混合浪状态时,一些频谱分析结果必须经过修正才能应用.同一海况下,海面波动的时间过程和沿主波向的空间分布是明显不同的.当海面有突发性大浪时,外频谱能够很好地反映不平稳海况,而频谱则把这种不平稳性平滑了.文章着重讨论了波长和波陡的计算、频谱和外频谱的差异.     

Wave Attenuation and Friction Coefficient on the Coral-Reef Flat

Several sets of S4 direction-wave-current-tide meters have been deployed on the coral-reef fiat of Yongshu Reef in the sea area of Nansha Islands. Based on the observational sea wave data, the attenuation characteristics of the waves propagating on the coral reef flat, the bottom friction coefficients and the transfer of wave energy are discussed in the paper. The results show that, in the relative depths of 0. 0613- 0.0867, the wave height attenuation per unit distance of wave propagation is 22.09 %-46.56%, with an average of 31.35 % ; the wave energy, attenuation coefficient, 33.74 %- 53.22%, with an average of 43.61%. The average of the bettom friction coefficients on the coral-reef flat is 0. 1346,which is about 10 times thai on the sand or silt bottom. In the couse of propagation on the reef flat, the waves sustain more loss in high frequency than in low frequency and the spectral energy transfers to the low frequency. These results may be used for reference in island and reef engineering.