基于类海啸波型的岛礁水动力特性数值模拟研究

Numerical investigation of hydrodynamic characteristics of fringing reef under the impact of tsunami-like wave

基于非静压单相流模型NHWAVE建立了高精度二维数值波浪水槽,采用日本2011年实测真实海啸波型系统研究了海啸波在岛礁上传播变形的规律,并且分析了波高、礁坪淹没水深和礁前斜坡坡度等因素对孤立波和真实海啸传播变形的影响。结果表明,相比孤立波,类海啸波的波长明显大于孤立波波长,在测点处引起的水面变化持续时间更长,同等波高情况下真实海啸波型比孤立波能够携带更多的能量,与岛礁的相互作用也更为复杂,在礁坪上形成的淹没水深约为孤立波的两倍。礁前斜坡坡度和礁坪淹没水深均对类海啸波的反射和透射系数有显著影响。随着礁前斜坡坡度的增加,反射系数和透射系数均逐渐增加。随着礁坪淹没水深的增加,反射系数逐渐减小,而透射系数逐渐增大。但是,反射系数和透射系数均随着入射波高的增加而逐渐减小。

Based on the nonhydrostatic single-phase flow model NHWAVE,a high-resolution numerical wave tank was established.The hydrodynamic characteristics of fringing reef under the impact of tsunami wave have been systematically investigated by parameterizing the tsunami wave profile observed during 2011 Japan earthquake and tsunami.Effects of several prominent factors,such as the incident wave height,the water depth at reef flat,and slope of reef front beach,are discussed in detail.It is found that the wave length of tsunami-like wave is much longer than that of solitary wave.At the same wave height,tsunami-like waves can carry more wave energy than solitary waves do,and their interaction with reefs is also more complicated.The submerged water depth formed on the reef caused by tsunami-like wave is approximately twice that of solitary wave.The slope of the reef front beach and the water depth at the reef flat submerged water both have significant influences on the reflection and transmission coefficients of tsunami-like waves.Both the reflection coefficient and the transmission coefficient slightly increase with the slope of reef front beach.The reflection coefficient slightly decreases with the water depth at reef flat.The transmission coefficient gradually increases with the water depth at reef flat.Meanwhile,both reflection and transmission coefficients gradually decrease with the increase of incident wave height.