Low frequency swash motion induced by wave grouping
Low frequency swash motion induced by wave grouping
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DOI：
10.1016/s0378-3839(97)81750-4
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发表时间：
1997-11
影响因子：
4.4
通讯作者：
T. Baldock;P. Holmes;D. Horn
中科院分区：
文献类型：
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作者：
T. Baldock;P. Holmes;D. Horn
本文研究了陡海滩上由波群直接诱导的冲浪的低频运动。提出了一种新的实验研究，它考虑了内碎波区和冲波区的水动力，使用垂直波计和一个助跑线。规则波，波群和随机波的结果进行了讨论，特别是参考低频运动。内碎波区和冲浪区被发现是不饱和的入射短波频率，因此，显着的波浪分组是明显的海岸线。发现碎波带中的低频运动与入射波组同相，因此可将其视为随时间变化的设置（沃森和Peregrine，1992）。的低频率运动的斜流被证明是一个数量级大于内冲浪区，不一致的跨岸驻波长波，其中没有证据被发现。我们证明，低频运动的海岸线提供了一个很好的近似助跑的个别钻孔，因此描述了助跑包络线。频谱分析表明，冲流的低频运动与离岸波高的调制直接相关，即入射波包络中的低频能量。此外，随机波浪上升谱显示f− 4高频滚降，如亨特利等人（1977）所发现的。积累的数据表明，除非碎波带完全饱和，否则低频旋转斜流运动的很大一部分可能直接归因于入射波分组，而不是驻波长波。
This paper concerns the low frequency motion of swash directly induced by wave grouping on a steep beach. A new experimental investigation is presented which considers the hydrodynamics of the inner surf zone and swash zone using vertical wave gauges and a run-up wire. Results for regular waves, wave groups and random waves are discussed, with particular reference to low frequency motions. The inner surf zone and swash zone are found to be unsaturated at incident short wave frequencies and, as a result, significant wave grouping is apparent at the shoreline. The low frequency motion in the surf zone is found to be in phase with the incident wave grouping and may therefore be regarded as a time varying set-up (Watson and Peregrine, 1992). The low frequency motion of the swash is shown to be an order of magnitude greater than that in the inner surf zone, inconsistent with cross-shore standing long waves, for which no evidence is found. We demonstrate that the low frequency motion of the shoreline provides an excellent approximation to the run-up of individual bores and therefore describes the run-up envelope. Spectral analysis shows that the low frequency motion of the swash is directly linked to the modulations in offshore wave height i.e. the low frequency energy in the incident wave envelope. In addition, the random wave run-up spectra show an f−4high frequency roll-off, as found by Huntley et al. (1977). The accumulated data show that, unless the surf zone is totally saturated, a significant proportion of the low frequency swash motion may be directly due to incident wave grouping and not standing long waves.