基于Navier-Stokes方程珊瑚岛礁附近孤立波传播变形数值模拟

Numerical investigation of solitary wave transformation over reef islands based on Naiver-Stokes equations

为了分析珊瑚岛礁附近的孤立波的传播变形特征,本文基于Navier-Stokes方程利用Open FOAM开源程序包建立三维波浪数值水槽,数值模型采用大涡模拟法(LES)模拟湍流和修正的流体体积法(VOF)捕捉自由液面,并通过文献中的实验数据进行了模型验证。相较于传统的沿水深积分的Boussinesq模型,该模型可以更为准确地模拟水平流速的垂向分布,并且对波浪破碎和干湿交界线的模拟不需要人为的干预。研究发现所采用的模型能够合理的模拟孤立波在珊瑚礁礁前斜坡上的浅化、礁缘附近的破碎以及破碎波在礁坪上的演化过程,并能适应礁前斜坡坡度和礁坪淹没水深的变化以及礁冠存在的情况。研究结果为进一步认识珊瑚礁对海啸灾害的防御作用提供参考。

To analyze the transformation and deformation characteristics of a solitary wave over reef islands,a threedimensional numerical wave tank is developed based on Navier-Stokes equations using the open-source software package Open FOAM. To capture the free surface,the LES turbulence closure solver is employed,together with the modified VOF method,and the numerical model is validated using experimental data in literature. Compared to the conventional depth-integrated Boussinesq model,it is possible to obtain the vertical velocity distribution associated with waves,and both the wave-breaking process and the wet-dry shoreline movement can be modeled without artificial treatment. Numerical results show that the adopted model can reproduce wave shoaling on the fore-reef slope and wave-breaking at the edge-reef,and can reproduce the evolution of breaking waves on the reef flat reasonably well. Furthermore,variations in reef profile and water depth,and the presence of reef crest can also be addressed by the model. These model results can be used as a reference in further studies investigating the role of coral reefs in tsunami mitigation.