珊瑚岛礁孤立波爬坡的平面二维数值模拟研究

2DH numerical study of solitary wave runup around a reef-lined island

为了探究岛屿周围珊瑚礁在抵御海啸灾害中的作用,采用激波捕捉类Boussinesq模型FUNWAVE-TVD,对孤立波在理想化三维岛礁地形上的传播及爬坡开展了现场尺度的平面二维数值模拟,分析了入射波高、礁坪水深、礁坪宽度、礁前斜坡坡度、礁后斜坡坡度、珊瑚礁糙率对岛屿四周孤立波爬高分布的影响。结果表明,珊瑚礁的存在总体上可有效降低岛屿四周孤立波的最大爬坡高度;入射波高、礁坪水深、礁坪宽度、珊瑚礁糙率是影响珊瑚岛礁四周孤立波爬坡分布的主要因素,岛礁四周最大爬坡高度会随入射波高和礁坪水深的增大、礁坪宽度和珊瑚礁糙率的减小而不断增大;当礁坪水深增大到一定程度时,珊瑚礁主要会对岛屿背浪面的爬高失去影响,而当礁坪宽度和珊瑚礁糙率减小至一定程度时,会出现岛礁四周最大爬高高于无珊瑚礁时爬高的现象;礁后斜坡的变缓会使岛礁周围的最大爬高有所减小,而礁前斜坡坡度对珊瑚岛礁周围的最大爬高几乎没有影响。

In order to investigate the role of coral reefs around an island in the mitigation of tsunami hazards,solitary wave propagation and runup around an idealized reef-lined island was modelled using the shock-capturing Boussinesq model,FUNWAVE-TVD.The influences of the incident wave height,reef flat water depth,reef flat width,fore-reef slope angle,back-reef slope angle and reef roughness on the run-up distribution around the island were investigated respectively.The results show that in general,the existence of coral reefs can effectively reduce the maximum solitary wave runup height around the island.The incident wave height,reef flat water depth,reef flat width and reef roughness are the main factors affecting the distribution of solitary wave runup around the reef-fringed island.The maximum runup heights around the reef-fringed island increase with the increase of incident wave height and reef flat water depth and the decrease of reef flat width and coral reef roughness.When the reef flat water depth increases to a certain level,coral reefs will mainly lose their influence on the runup in the back of the island.When the reef flat width and the reef roughness are reduced to a certain level,the maximum runup heights around the reef-fringed island can be higher than that around the island without fringing reefs.The maximum runup around the island will decrease a little as the back-reef slope becomes gentle,while the fore-reef slope has little effect on the maximum runup height around the island.