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基于流体动力学的泥石流运动过程及冲击力学研究
Alternative TitleRunout and Impact Analysis of Debris Flow Based on Computational Fluid Dynamics
Language中文
吴恒滨
Thesis Advisor何思明
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline岩土工程
Keyword泥石流 流变模型 Bingham模型 流固耦合 冲击力学 能量守恒 深度平均方程
Abstract泥石流灾害在我国西部山区非常普遍,对人们生命财产及基础交通设施造成严重危害。然而,目前我国泥石流灾害研究基础还比较薄弱,减灾防灾能力还难以满足国家经济建设和公共安全的需要,主要体现在泥石流灾害危害范围预测和泥石流灾害与承灾体动力相互作用等方面。基于此,针对我国泥石流灾害减灾技术方面存在的问题,采用深度积分方法、双层流方法、能量守恒法和多相流法等四种方法,系统研究泥石流灾害动力过程与冲击力学,主要包括: 基于传统深度平均方程,选取典型泥石流基底摩阻力模型,采用Matlab编制拉格朗日差分程序,通过算例分析了泥石流运动时间、运动距离和堆积形态等关键参数。计算结果表明:现有基底摩阻力模型可以分为两大类:Coulomb模型和Bingham模型,其余均为演化方程;流变模型的选取很大程度上依赖泥石流浆体组成性质以及泥石流运动过程中颗粒粘性、塑性、碰撞等因素的比重。 基于非牛顿流体力学模型,对泥石流分两层进行深度积分,考虑粘性泥石流物理力学特性,和剪切区的土压力系数,对泥石流运动控制方程进行改进;重点研究了屈服应力、基底倾角、土压力系数等因素对泥石流运动特性的影响。结果表明:基底倾角对泥石流运动时间和距离影响显著;土压力系数和沿深度变化的屈服应力主要影响泥石流运动时间。 基于流体力学能量方程,以泥石流微元条为研究对象,分析了泥石流运动过程中的动能、重力做功和变形能,引入耗散能的概念,把热能转化为表面力做功,并考虑了降雨和浆体对固体颗粒摩擦造成的能量损失,建立了泥石流运动的控制方程。计算结果表明:降水雨强能量对泥石流的影响主要体现在其运动形状上,对运动时间基本没有影响;浆体对固体颗粒摩擦导致的能量损失很大程度上缩短了运动时间和运动距离,尤其体现在泥石流最大运动距离方面。 传统多相流模型一般把泥石流考虑为水和砂的混合物,基于现有研究成果,提出了一种改进的泥石流流变模型,研究了泥石流运动模型边界条件,采用Visual Studio 2010对FLUENT程序进行二次开发,通过室内模型试验验证了该方法的可靠性;进一步,通过梁家山沟泥石流对改进流变模型进行分析,和现场调查资料结果较为一致。 现有泥石流冲击研究多集中在泥石流冲击力的理论解析和数值计算方法,引入流固耦合理论,采用ANSYS Workbench软件system coupling模块,对室内冲击挡板模型试验进行分析。结果表明: BVP流变模型的运动形状和冲击力大小较传统Bingham模型更加符合实际。流固耦合方法可以直接得到结构物动态力学响应,如基底约束反力和弯矩、结构物位移、应力和应变等力学指标,可为泥石流灾害防治工程设计提供理论依据。
Other AbstractDebris flow and landslide are common disasters in mountain regions of western China, which seriously threaten people’s life and damage infrastructures. In present, however, researches on debris flow disaster in China are weakness, and the capability of prevention and reduction of disaster cannot meet the economic development and public security, especially in the runout and impact analysis of debris flow. Base on this, according to the existent problems in the techniques of prevention and reduction of disaster, the runout and impacting mechanism of debris flow are systematic studied in this paper and include, Based on the depth averaged equations widely used in debris flow, the typical basal resistance relationships are selected, the run time and distance of debris flow are analyzed by using the lagrange difference method; the simulated results show that, the present resistance relationships can be divided into two categories, Coulomb model and Bingham model, the other models are the deductive models; the rheological model depends on the grain composition of debris flow and the proportions of viscosity, plastic, and collision in the motion of debris flow. Based on the Non-Newtonain fluid model, debris flow is divided into two layers and integrated, taking the physical characteristics of viscous debris flow and the earth pressure coefficient in shear zone into account, the improved mathematical model of debris flow is verified by the case of debris flow in an inclined plane. Compared with the depth averaged equations, the model exhibits the two layer characteristics of debris flow, and can include the cohesion, apparent friction angle and earth pressure coefficient. Based on the equations of energy conservation in computational fluid dynamics, the slice of debris flow is studied, and the kinematic energy, work done by gravity and deformation is analyzed; the work done by heat conduction is transferred to surface stress by introducing the dissipation energy; the rainfalls and energy loss caused by friction forces impact on grain are considered, and the equations of motion are established. The sample analysis results show that, the effect of rainfall energy on the motion of debris flow mainly reflects the shape of debris flow, while the effect of energy losses caused by the grain-fluid friction on the debris flow reflects the time and distance of debris flow to a certain extent. Debris flow is considered as the mixture of water and sand in the traditional multi-phase flow, in this paper, the UDF is adopt to make the secondary development of Fluent code, the rhological models and boundary conditions are emphasized, by analyzing the Bingham flow test, this method is verified. Furthermore, the Liangjiashan gully debris flow is simulated with the BVP rheological model, and the simulated results are consistent with the investigate data. The present methods of debris flow impacting are mainly focuses on the analytical method and simulation of impact force, the Fluid-Structure Interaction method is introduced, the system coupling model of ANSYS Workbench software is used to simulate the motion and impact of granular flow. The simulated results show that, the BVP model is more reasonable than the Bingham model for the shape of debris flow and impact forces. The FSI method can directly obtain the mechanical characters of structure, such as the reaction of force, moment and displacements, stresses and strains of structure, which can guide the optimal design of preventing engineering.
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7935
Collection山地灾害与地表过程重点实验室
Recommended Citation
GB/T 7714
吴恒滨. 基于流体动力学的泥石流运动过程及冲击力学研究[D]. 北京. 中国科学院研究生院,2014.
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