孤立卷破波传播演化特征分析

Characteristics of propagation and evolution of plunging solitary waves

卷破波是海洋中极具破坏性的波浪,传播演化过程复杂。本文采用物理试验方法对孤立卷破波演化特性进行研究。在二维水槽通过浅水作用生成孤立卷破波,且选取不同水深和入射波高,采用高速摄像机对波面进行捕捉,进而基于采用开源计算机视觉库OpenCV进行图像处理及分析。结果表明:卷破波卷舌形成后,卷舌内侧波面部分区域逐渐不稳定,并出现褶皱和轮廓弯曲,随后发展成水体全部脱落形成水滴或者部分脱落形成水线;OpenCV能够提取卷破波波面轮廓,且发现孤立卷破波尚未卷曲的前部波面轮廓能够保持较好的形态不变性;另外,当入射波陡增加,卷舌冲击自由液面的卷曲角度越大,卷舌演化距离越长,卷入水中气体也越多。

Plunging waves,which can induce destructive power in the sea,have complex propagation processes.Experiments were carried out to get an insight into the evolution characteristics of plunging solitary waves.First,solitary waves were generated in a wave flume,subsequently evolving into plunging waves via the shoaling effect.Besides,various water depths and wave heights were selected before recording images of the wave propagation process using a high-speed camera,and an image analysis based on the open-source computer vision library,OpenCV,was then used to extract and analyze the wave surface contours.The results showed that through the images after the plunging jet forms,instabilities at the inner surface were found.These instabilities then caused the water drop due to complete shedding or formed water thread due to partial shedding.The OpenCV can extract the surface contours of breaking waves,and it showed that the wave surface contours of solitary plunging waves prior to breaking could remain constant,which worked for different water depths and heights.In addition,as the steepness of the wave increased,the plunging jet evolved with a longer distance and showed a more inclined angle as imping on the free water surface,thus swallowing more air into the water.