基于河流阻力规律的河型参数化分类方法与河型演变特征研究

发布时间：2018-09-19 10:44

【摘要】：在制定河流保护和水资源开发计划之前,应该最大限度地掌握河流相关信息,以做到合理科学地规划河流。自然界天然河流虽然复杂多变,但又遵循一定的规律,一些河流形状呈现出规则且极相似的一面,河流形态是河流动力的外在体现,也是河流自然演变规律的重要表现形式。本文从河流阻力规律出发,对河流平面形态的河型分类进行了研究,建立了基于阻力规律的河型参数化分类方法,对河流自然演变中最重要的弯道水动力结构进行了数值模拟和实验研究,对不同参数下可能存在的河型及其演变过程进行了实验研究。文章中采用了统计分析、理论分析和模型试验等多种研究方法。文章主要内容和创新之处:1)构建河流阻力规律关系式。天然河流阻力规律决定着河流的平面形态,不同河型特征反映了不同的河流阻力规律。有别于水流在明渠中阻力规律形式,通过考虑河流形态因素,构建河流阻力规律关系式,具体方法是:将沿程水头损失公式向天然河流推广,利用坡降、流量、流速、泥沙粒径、河流形态、河道几何特征等一系列参数,通过资料分析、数据拟合等技术手段,得到了河流阻力规律的表达形式。将河型参数作为分类指标,反演河流阻力规律表达形式,建立了一种物理概念明确、表达简单的河型分类方法。用两条阈值曲线将整个河流系统分成单线型、不稳定多线型、稳定多线型等三大类型。通过研究发现,河型分类系统中单线型河道对河岸强度相当敏感,而多线型河道并不直接受河岸强度影响,尤其是大宽深比的情况。在外部扰动影响下,河流类型可以发生短暂的变化,如弯曲型河道出现游荡特征,但其最终能够回到原始平衡状态类型。2)典型弯道水流结构研究。弯曲河道是最为基础的河流形态,是顺直明渠最简单的变形,弯道水流运动也是河型演变的源动力。通过研究,已知天然河流局部河道迁移速率在曲率半径R与河道宽度B比率接近3时最大,针对这一现象,本文从数值模型和物理模型两方面研究了该临界弯曲度下的常曲率弯道水流动力特征,包括该临界情况下的各种流速分量、流线、二次流和壁面切应力等。通过数值与弯道水槽实验比较,证实RNG k-ε模型能够高效地模拟弯道水流结构,同时也进一步证明弯道水流受到二次流强烈的影响。3)河型演变的实验研究。不同河型间的交替转化,伴随着河流阻力规律的变化,现实河流中表现为水流结构、坡降、粒径分布、河岸线及床面形态等各种参数特征的变化。在实验室条件下,对正弦派生曲线弯道短期演变规律进行了研究,控制变量包括:初始河道弯曲度、河宽以及水流流量;实验测量结果包括:河岸线、流场、地形和泥沙输移情况等。实验过程中不同工况下的河道有着不同的发展特征。用非粘性泥沙作为实验材料,实验河道易向着游荡型方向发展,而环境温湿度被证明也可以通过影响材料凝聚力而影响到河流演变进程。河道中出现的沙洲形态,反映了水流动力条件与河相关系的适应程度。本研究获得的实验结果在未来能帮助验证河型分类公式,为大型天然河流的平面形态演变研究提供支持。
[Abstract]:In order to plan rivers reasonably and scientifically, we should grasp the relevant information of rivers to the greatest extent before making plans for river protection and water resources development. Based on the law of river resistance, this paper studies the classification of river types in plane form, establishes a parametric classification method of river types based on the law of resistance, and carries out numerical simulation and Experimental Research on the most important bend hydrodynamic structure in river natural evolution. In this paper, statistical analysis, theoretical analysis and model test are used. The main contents and innovations of the paper are as follows: 1) Constructing the relationship between river resistance laws. The resistance laws of natural rivers determine the plane shape of rivers and the characteristics of different river types. Different from the law of resistance of water flow in open channel, the relationship of resistance law of river is constructed by considering the factors of river morphology. The specific method is to generalize the formula of head loss along the river to natural river, and make use of a series of parameters such as slope, discharge, velocity, sediment particle size, River form, River geometric characteristics and so on. By means of data analysis and data fitting, the expression form of river resistance law is obtained. Taking the river type parameters as classification index, the expression form of river resistance law is inverted, and a river type classification method with clear physical concept and simple expression is established. It is found that the single-line channel is very sensitive to the strength of the riverbank, while the multi-line channel is not directly affected by the strength of the riverbank, especially in the case of large aspect ratio. The curved channel is the most basic river form and the simplest deformation along the straight open channel. The flow movement in the curved channel is also the source power of the evolution of the river pattern. In view of this phenomenon, the flow dynamic characteristics of a curved channel with constant curvature under the critical curvature, including various velocity components, streamlines, secondary flow and wall shear stress, are studied by numerical and physical models. -e model can simulate the flow structure of curved channel efficiently, and it also proves that the flow in curved channel is strongly influenced by secondary flow. 3) experimental study on the evolution of river type. The alternate transformation of different river types, accompanied by the change of river resistance law, manifests itself as flow structure, slope, particle size distribution, riverbank and bed shape in real river. The short-term evolution of sinusoidal curved bends is studied under laboratory conditions. The control variables include initial curvature, river width and flow rate. The experimental results include: riparian line, flow field, topography and sediment transport. With non-cohesive sediment as experimental material, the experimental channel tends to develop in a wandering direction, and the environmental temperature and humidity have been proved to influence the evolution process of the river by affecting the cohesion of the material. The experimental results will be helpful to verify the classification formulas of river types in the future, and provide support for the study of the evolution of plane morphology of large natural rivers.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV147

【相似文献】