我国是世界上拥有水库数量最多的国家，由于自然灾害或者人为因素，大坝决堤事件时有发生。溃坝会对人们的生命及财产安全造成极大的威胁，因此关于该问题的研究一直是广大学者关注的热点。由于溃坝流的强非线性瞬态冲击特性，解析研究并不适用。近年来，随着计算机技术的不断发展和数值算法的不断进步，数值模拟不失为一种经济可行的研究手段。光滑粒子流体动力学(Smoothed Particle Hydrodynamics, SPH)方法是一种拉格朗日型的无网格粒子法。与传统的基于网格的数值方法相比，它是用一组插值点来离散问题域，无需网格，因此适宜模拟溃坝流流动问题。但SPH方法也存在以下缺点，限制了其向更复杂问题的应用：①复杂几何形状的边界条件不宜施加；②传统SPH方法存在压力伪振荡的问题，会影响溃坝对下游结构物冲击力的分析；③由于SPH方法自身的拉格朗日特性，流体粒子在流动过程中存在粒子分布不均的问题，从而影响问题求解的计算精度。

本论文提出了一种改进SPH方法用于溃坝流问题的数值模拟，通过与传统SPH方法结果的比较，展现了改进SPH方法的优势，并通过与文献结果的比较验证了改进SPH方法的有效性；然后应用改进SPH方法对溃坝流冲击不同障碍物问题进行数值模拟研究，分析了不同形状的障碍物对溃坝的阻碍效果。本论文主要工作如下：

(1) 提出了一种改进SPH方法，其改进之处在于：①针对SPH方法复杂几何形状边界条件不宜施加的问题，结合现有的虚粒子法和镜像粒子法，提出了一种能适用于任意复杂形状的边界处理技术。②为解决传统SPH方法的压力伪振荡问题，在连续性方程中添加与密度相关的修正项，获得了精确不振荡的压力。③为消除粒子在流动过程中出现的分布不均缺陷，发展了一种粒子微迁移技术。该技术通过快速精确地定位自由表面粒子并施加合理的速度偏差，以保证粒子的均匀分布。

(2) 应用改进SPH方法对溃坝流问题进行数值模拟，通过与传统SPH结果的比较，表明本论文提出的改进SPH方法能够获得精确不振荡的压力分布，能够获得流动过程中的均匀粒子分布。这些有利于提高数值模拟结果的准确性及分析溃坝对下游结构物冲击力的置信度，从而展现出改进SPH方法的优势。文中分析了不同粒子数目对计算结果的影响，结果表明改进SPH方法具有良好的收敛性。另外，运用该方法获得了溃坝前沿位置随时间的变化及右侧固壁压力随时间的变化图，通过与实验结果和文献结果的比较验证了改进SPH方法模拟自由表面流动问题的有效性。

 (3) 将改进SPH方法成功推广到溃坝冲击不同障碍物的数值模拟中，分别考虑了柱形、有孔柱形、锲形、半圆形、四分之一上半圆形和四分之一下半圆形障碍物这六种情形，比较了未添加障碍物和添加不同障碍物的溃坝水流动向和流体前沿，研究了不同形状的障碍物对流动速度和右壁边界处受到的压力影响，分析了不同形状障碍物对材料强度上的需求以及对水流的阻碍效果。

本论文可为溃坝自由表面流动问题的数值模拟研究提供一种不依赖于网格的新研究思路，其数值模拟结果对溃坝预警、溃坝水流动向以及溃坝下游区域的结构设计具有一定的指导意义。

Our country is the country with the largest number of reservoirs in the world. Due to natural disasters or man-made factors, dam bursts often occur. Dam failure will pose a great threat to people's life and property safety, so the research on this problem has always been the focus of attention of scholars. Analytical studies are not applicable due to the strong nonlinear transient shock characteristics of dam-breaking flows. In recent years, with the continuous development of computer technology and the continuous progress of numerical algorithms, numerical simulation can be regarded as an economical and feasible research method. The Smoothed Particle Hydrodynamics (SPH) method is a Lagrangian-type meshless particle method. Compared with the traditional grid-based numerical method, it uses a set of interpolation points to discretize the problem domain without grid, so it is suitable for simulating dam-breaking flow problems. However, the SPH method also has the following shortcomings, which limit its application to more complex problems: ①The boundary conditions of complex geometric shapes should not be applied; ②The traditional SPH method has the problem of pseudo-oscillation of pressure, which will affect the impact force of the dam break on the downstream structures. Analysis; ③Due to the Lagrangian characteristics of the SPH method itself, the fluid particles have the problem of uneven particle distribution in the flow process, which affects the calculation accuracy of the problem solving.

In this paper, an improved SPH method is proposed for numerical simulation of dam-breaking flow problems. By comparing the results with the traditional SPH method, the advantages of the improved SPH method are shown, and the effectiveness of the improved SPH method is verified by comparing with the results of the literature. Then, the improved SPH method is used to carry out numerical simulation research on the problem of dam-breaking flow impacting different obstacles, and the hindering effect of obstacles of different shapes on dam-breaking is analyzed. The main work of this paper is as follows:

(1) An improved SPH method is proposed. The improvements are as follows: ①Aiming at the problem that the boundary conditions of complex geometric shapes in the SPH method are not suitable to be applied, combined with the existing virtual particle method and mirror particle method, a new method that can be applied to the SPH method is proposed. Boundary processing techniques for arbitrarily complex shapes. ②In order to solve the pressure pseudo-oscillation problem of the traditional SPH method, a correction term related to the density was added to the continuity equation, and an accurate and non-oscillating pressure was obtained. ③ In order to eliminate the uneven distribution of particles in the flow process, a particle micro-migration technology was developed. The technique ensures uniform distribution of particles by rapidly and precisely locating free-surface particles and applying reasonable velocity deviations.

(2) The improved SPH method is used to numerically simulate the dam-breaking flow problem. By comparing with the traditional SPH results, it is shown that the improved SPH method proposed in this paper can obtain accurate and non-oscillating pressure distribution, and can obtain uniform particle distribution in the flow process, which is beneficial to improve the accuracy of numerical simulation results and analyze the confidence of the impact force of dam failure on downstream structures, thus showing the advantages of improving the SPH method. The influence of different particle numbers on the calculation results is analyzed, and the results show that the improved SPH method has good convergence. In addition, the change of the position of the dam-breaking front and the change of the right solid wall pressure with time are obtained, and the effectiveness of the improved SPH method to simulate the free surface flow problem is verified by comparing with the experimental results and the literature results.

 (3) The improved SPH method was successfully extended to the numerical simulation of different obstacles impacted by dam break, and the cylindrical, perforated cylindrical, wedge, semicircle, quarter-upper semicircle and quarter-point were considered respectively. One of the six cases of lower semicircular obstacles, compared the flow direction and fluid front of the dam-breaking water without adding obstacles and adding different obstacles, and studied the effect of obstacles of different shapes on the flow velocity and the impact on the boundary of the right wall. The influence of pressure is analyzed, and the requirements for material strength and the blocking effect on water flow of obstacles of different shapes are analyzed.

This paper can provide a new research idea independent of grid for the numerical simulation of dam break free surface flow. The numerical simulation results can have a certain guiding significance for dam break early warning, dam-breaking flow trend and the structural design of the downstream area of dam break.

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