实验室观测条件下的规则长波对风浪低频频移影响

摘要

The influence of long regular waves on wind waves are examined in the laboratory tank. The wave spectra of wind waves are compared when there is and there is not long waves. Besides the widely addressed suppression of wind waves by long waves, it is also found that, the presence of long regular wave induces low frequency shift of wind waves when long wave slope is smal and also its frequency fl is quite apart from wind wave crest frequencies f p . The effect of long wave modulation on wind wave spectra is estimated according to Longuet-Higgins&Stewart (1960) (abbreviated as LS60 afterwards),which is found to be prominent at the large ratio of p lf f . It’s also found that, when the limitation of wave breaking on wind wave steepness is taken account of, the LS60 theory can explain the low frequency shift satisfactorily. The work suggests that, at smal long wave slope and large ratio of p lf f , the LS60 modulation mechanism together with the enhanced wave breaking may dominate the influence of long waves on wind waves.%本文利用实验室波浪水槽观测规则长波对风浪的影响。谱分析显示，较之纯风浪谱，除已被广泛关注的长波抑制风浪这一现象外，当长波波陡较小，且频率远离风浪峰频时，长波还使得风浪谱向低频移动。本文利用Longuet-Higgins & Stewart（1960）理论，并考虑到风浪破碎的约束，计算了规则长波的存在对风浪谱的影响，发现可以较好地解释这一现象。这一工作表明，当长波波陡小且频率远离风浪峰频时，长波对短波的二阶调制及其引起的破碎加强可能是长波影响风浪的主要机制。