浅水极限波浪几何特征的实验研究

Laboratory study on geometric characteristics of limitting waves in shallow water

该文通过物理模型实验,对浅水区域内的波浪在破碎前极限状态下的几何特征进行了研究。实验基于JONSWAP谱对不规则波浪进行模拟,通过对波群中出现的单体极限波浪进行捕捉并对波形进行测量而得到研究样本。为了考察底坡因素对极限波浪几何特征的影响,实验共考虑了3组大小分别为β=1/15、1/30以及1/45的地形坡度。统计结果表明,在实验所采用的坡度范围内,当地波高与水深对近岸极限波浪的影响最为显著,随着水深与波高因素变化,极限波浪的几何特征也出现明显的改变。坡度因素对极限波陡和偏度的影响很小,可以被忽略,但是对不对称度参数的影响相对比较明显,坡度越陡,不对称程度越剧烈。最后,通过参数化,本文给出了极限波浪几何特征变化的经验公式。

Physical experiments were carried out in a wave flume to examine the geometric characteristics of limiting gravity waves propagating in shallow water. Several random wave trains varying height and peak frequency were generated using JONSWAP spectra. Three bottom slopes （1/15, 1/30, 1/45） were installed in the wave flume and the influence of slope bottoms were also considered. Limiting waves were captured from the measured wave trains and the geometric characteristics of its waveform were analyzed. It is found that in the range of bottom slope adopted in this experiment both initial wave heights and local water depth have significant influence on the limiting characteristics of shallow water waves. With the influence of these factors, the geometric of extreme waves are de- veloped. The bottom slopes effect to the limiting steepness and skewness could be neglected, however, it has obvi- ous influence to the limiting wave asymmetry. It will show a more severe asymmetry when waves are on a steeper bottom. Furthermore, the empirical formulae regarding the relationships between geometric characteristics and the local nondimensional wave height were derived.