海啸数值模拟及其对近岸桥梁上部结构波浪力研究

发布时间：2018-03-31 12:41

本文选题：海啸　切入点：显式算法　出处：《哈尔滨工业大学》2017年博士论文

【摘要】：海啸是一种破坏力极强的自然灾害。当海啸在近岸登陆时由于携带巨大的能量,将会对沿海基础设施产生很大的破坏力,严重影响沿岸居民生活。为了减小海啸对近岸居民生命财产的威胁,全球多个国家开展了海啸预警研究,以达到对海啸进行预警的目的。目前国际上主流的海啸预警主要采用浅水方程与实测数据相结合的模型。在海啸的预警中数值模型的计算时间非常重要,较快的数值模型能够节省预警时间,从而减小海啸所带来的灾害。桥梁作为近岸重要的交通枢纽,在海啸发生时很容易受到波浪的冲击从而产生破坏,因此研究近岸桥梁在海啸作用下的受力形式和破坏机理具有重要的意义。本文基于数值模拟和水动力试验对上述问题进行了研究,主要内容如下:(1)将求解波动方程的显式数值算法引入到海啸数值模型COMCOT中,从而加快海啸模型的计算速度。为了使显式的海啸数值模型能够模拟海啸的近岸爬高,将求解线性浅水方程的显式算法和求解非线性浅水方程的有限差分方法相结合,提出了新的网格之间的嵌套算法。并利用2004印尼海啸对算法的有效性进行验证。(2)对于以浅水方程为控制方程的海啸模型,如何考虑海啸传播过程中的色散性问题,一直是围绕浅水方程模型的热点研究方向。本文主要聚焦在如何使显式的数值算法能够在常网格条件下满足海啸在变化地势传播过程中所包含的色散问题。为了达到这一目的,由显式数值模型出发引入一个可变参数,推导了新的色散算法和相应的色散条件,用来应对地势的变化,使海啸在可变地势条件下传播中的物理色散可以由常网格条件下的数值色散考虑,简化了色散条件,提高了计算效率。(3)采用孤立波替代海啸,试验研究了桥梁上部结构形式、净空和波高对波浪力的影响规律。试验中研究了五种不同桥梁上部结构形式,在三种净空高度和四种波浪幅值条件下所受波浪力的特征,并通过在桥梁上部结构设置通气孔研究了通气孔对桥梁所受波浪力的抑制效果。(4)利用开源数值软件OpenFOAM建立了桥梁在海啸作用下的数值模型,并开展了数值模拟研究,研究了不同形状的桥面板与波浪作用过程的流场特征。通过流场分析确定了桥梁在波浪作用下的破坏机理。同时,利用数值模型研究了防撞墙对波浪与桥面板之间流场的影响,揭示了防撞墙对所受波浪力的影响规律。此外,利用数值模型研究了通气孔对流场的影响及其波浪力抑制原因,分析了通气孔的形状、大小和位置对桥梁所受波浪力的影响规律。
[Abstract]:A tsunami is a very destructive natural disaster. When a tsunami makes landfall on the shore, it will have a great deal of damage to coastal infrastructure because of its enormous energy. Seriously affecting the lives of coastal residents. In order to reduce the threat of the tsunami to the lives and property of inshore residents, many countries around the world have carried out tsunami warning studies. In order to achieve the purpose of tsunami warning, the current mainstream tsunami warning model mainly uses shallow water equation and measured data. The calculation time of numerical model is very important in tsunami early warning. The fast numerical model can save the warning time and reduce the disaster caused by the tsunami. As an important transportation hub near the shore, bridges are vulnerable to waves and damage when the tsunami occurs. Therefore, it is of great significance to study the force form and failure mechanism of near-shore bridge under the action of tsunami. The above problems are studied in this paper based on numerical simulation and hydrodynamic test. The main contents are as follows: 1) the explicit numerical algorithm for solving wave equation is introduced into the tsunami numerical model (COMCOT) to speed up the calculation of the tsunami model. The explicit algorithm for solving linear shallow water equation is combined with the finite difference method for solving nonlinear shallow water equation. A new nesting algorithm between meshes is proposed, and the effectiveness of the algorithm is verified by the 2004 Indonesian tsunami. How to consider the dispersion problem in the tsunami propagation process for the tsunami model with shallow water equation as the governing equation. This paper focuses on how to make the explicit numerical algorithm satisfy the dispersion problem in the process of the tsunami propagating in the changing terrain under the condition of constant grid. In order to achieve this purpose, this paper focuses on the research direction of the shallow water equation model. Based on the explicit numerical model, a variable parameter is introduced, and a new dispersion algorithm and corresponding dispersion condition are derived to deal with the change of terrain. The physical dispersion of tsunami propagating under variable terrain condition can be considered by numerical dispersion under constant grid condition. The dispersion condition is simplified, and the calculation efficiency is improved. The influence of clearance and wave height on wave force. The characteristics of wave force under three clearance heights and four wave amplitudes have been studied in the experiment of five different bridge superstructure forms. By setting the ventilation holes in the superstructure of the bridge, the suppression effect of the ventilation holes on the wave force of the bridge is studied. (4) the numerical model of the bridge under the action of the tsunami is established by using the open source numerical software OpenFOAM, and the numerical simulation research is carried out. In this paper, the characteristics of flow field of bridge deck with different shapes are studied. The failure mechanism of bridge under wave action is determined by flow field analysis. At the same time, the effect of collision wall on the flow field between wave and deck is studied by using numerical model. The influence of the wall on the wave force is revealed. In addition, the influence of the ventilation hole on the flow field and the reason of wave force suppression are studied by using the numerical model, and the shape of the ventilation hole is analyzed. The influence of the size and position of the bridge on the wave force.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：U441;TV139.26

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