离岸流灾害水动力学过程的数值模拟研究

离岸流是近岸流的重要组成部分，当波浪受到特殊海滩地形的影响，会形成一股沿着离岸方向运动的高速水流，能够迅速将人带离海岸，对海滨安全造成威胁。为了深入探究离岸流的形成机理及水动力学特性，本文基于二阶Stokes波浪理论，采用了更为光滑的变截面沙坝模型，通过流体体积法捕捉自由液面，对离岸流进行三维数值模拟探究。本文重点分析了离岸流产生时流场的瞬时速度、时均速度、压强等不同参量的分布规律，结果显示在沙坝和海岸线之间，有一对方向相反的水循环体系；对比不同流层离岸流的速度，了解到波浪与离岸流的耦合作用；并探究了入射波波高对离岸流强度及分布区域的影响，深化了对离岸流水动力学过程的认识。

Numerical simulation of the hydrodynamic process of rip current hazard

Rip current is an important part of nearshore current. Affected by special beach topography, waves will form a high velocity flow moving along the offshore direction, which can quickly take people away from the shore and pose a threat to beach safety. In order to further explore the formation mechanism and hydrodynamics characteristics, three-dimensional numerical simulation of rip current was carried out. In this paper, based on the second-order Stokes wave theory, a typical sandbar model with variable cross-section is adopted and used to generate rip current. The free liquid surface is captured by volume of fluid method. The rip current flow field distribution laws of instantaneous velocity, time-averaged velocity and pressure are analyzed and made some discoveries: there is a pair of opposite water circulation systems between the bar and the shoreline. By comparing the velocity distribution of rip current a different depth, the interaction between waves and rip currents is understood. Furthermore, the influence of incident wave height on intensity and distribution of rip current is also studied, which deepens the understanding of the hydrodynamic process of rip current.