泥石流与主河的汇流机理及泥石流运动的数值模拟

【作者】 胡健；

【导师】 匡尚富；

【作者基本信息】 中国水利水电科学研究院 ， 水力学及河流动力学， 2002， 硕士

【摘要】 泥石流与主河交汇问题是流体运动研究领域的一个新课题。它研究不同流体汇流产生的相互作用，处于牛顿流体运动研究和非牛顿流运动研究的交叉点。 本文首先研究了整个泥石流流域上发生的汇流现象，从泥石流产生区、流通区以及堆积区对泥石流汇流的形式和特点进行了总结。将泥石流汇流按流体物理性质重新分类，给出三种基本汇流形式。在此基础上，讨论了泥石流汇流与水流汇流的关系。 泥石流与主河汇流造成的灾害严重而且机理复杂。本文系统地总结了泥石流与主河汇流的运动方式、冲刷形式、汇流结果和沉积特征，阐述了泥石流汇入主河时的运动特点。研究分析泥石流潜入水下运动的机理和受力，考虑交界面动水压力的影响，给出泥石流水下运动的受力表达式。结合泥石流水下运动特点，讨论水下泥石流的交界面稳定问题和交界面上的泥沙交换，给出交界面失稳判别式。探讨泥石流堵河的影响因素和堵河体的形式，提出新的堵河判别条件。 在探讨入汇机理的基础上，认为粘性泥石流入汇对主河的影响主要体现在河床地形的改变。将粘性泥石流与主河的汇流视为分层流研究，上层为主河水流模型，下层为水下泥石流运动模型。由两者之间的相互关系，在水下泥石流运动模型中考虑水流动水压力和剪切阻力的影响，在水流模型中考虑泥石流入汇产生的地形影响，推导出二维粘性泥石流入汇主河的基本方程，并讨论了方程中参数的选取问题，运动阻力项参考结构二相流单流体模型的阻力表达式给定。 对主河无水流情况下的泥石流运动(即沟道泥石流运动)进行了数学模拟。数学模型采用一种基于三角网格的显式差分格式—有限节点法。这种方法将有限元的思想与有限差分的方法结合起来，吸收了有限元方法中三角网格模拟边界条件符合实际情况的优点，又具有差分方法计算量小的特点，方法的适用性经过了大量工程实践的检验。同时，此方法是显式差分格式，能够方便地处理交汇区的动边界问题。 本文在数学模型的调试与开发中，加入了可视化计算方面的工作，使计算结果更加直观。对于计算量大、费时长和平面形态复杂的数学模拟，实时图形显示和控制能够大大提高计算效率。 为了验证二维粘性泥石流运动数学模型的正确性，以泥石流小型堆积模型试验为模拟对象，计算模拟在不同来流方式、堆积区坡度和泥石流容重情况下的泥石流堆积范围。结果表明，粘性泥石流结构二相流模型对于一次来流堆积情况的模拟符合较好。由于缺乏合理的多次堆积模式，对于泥石流多次来流的累加堆积情况不适用。更多还原

【Abstract】 The mechanism of confluence between debris flow and main river, which discuss reciprocity between different liquids, is a brand-new question for fluid mechanics study. It includes not only research of Newtonian fluid, but also study of non-Newtonian fluid.Based on junction phenomena over debris areas, types and features at conflux of different areas are obtained. And then, three converging modes are classed by fluid qualities. The relations of debris flow and water flow at conjunctions are discussed in this paper.When debris flows converge into river, serious hazards and complex mechanisms will be caused. The movement types of debris flow, erosion shapes, results of confluence and deposition character in the conflux are summarized in this paper. The process of debris flow converging into main river is also presented. Based on the analysis of mechanism of debris flow under water, the stress expresses of debris flow under water are worked out by considering of moving water compressive stress. Combined with movement character of debris under water, the stabilization and material translation over interface of two fluids is discussed. The critical conditions of interface stabilization are made. A new criterion for blockage of main flow is obtained by approaching to the influence factors and the modes of blockage.The confluence between viscous debris flow and river flow considered as density flow is based on the assumption that the main influence of converging into water flow is the transform of riverbed. Therefore the upper layer is water flow and the nether layer is debris flow. The moving water compressive force and the shear force of interface are taken into account. An affluence model for debris flow and river is established by using this assumption. The equations of the model are approximately applied for simplicity. The bed resistance is obtained by express of the single-fluid model for debris flow.In this paper, a model of debris flow is calculated by using the finite nodes method with triangle cells. The method is combined with FDM and FEM. Vast applications proved that it can suit for complex boundary as FEM and is efficient as FDM. Moreover, it can expediently deal with moving boundary.The method of numerical simulation visualization make it easy for calculative results. Especially, real-time graphical display and control can make higher efficiencyfor numerical simulation, which has a complicated topography and needs a great calculative time.A 2-D model for debris flow is tested by experimental data of debris flow deposition. The plane extent, maximum length and width of the alluvial fan are computed under different conditions of supply process, initial ground slope and flow density. It shows that the model has a good agreement for single-supply alluvial experiment. But the model isn’t suit for multiple alluvial experiment.更多还原