顺直型复式河道断面的水力学特性研究

发布时间：2018-04-03 16:06

本文选题：复式断面　切入点：SERC-FCF　出处：《西安理工大学》2017年硕士论文

【摘要】：天然河道多为复式河道,其横断面通常由滩地和主槽两部分组成。在枯水季节,水流主要集中在河道的主槽中流动;当洪水来临时,水流会漫过河道滩地,形成漫滩水流。相比单一断面,复式断面的水流运动更加复杂。当水流漫滩后,主槽与滩地上两部分水体之间相互作用,断面水流的流速分布、床面剪切应力和阻力等水力因素都将发生变化,单一断面的水流计算公式已经不再适用,需要研究新的方法来描述复式断面的水流运动,因此研究复式断面的水力学特性具有重要意义。本文结合英国科学工程研究协会洪水水槽设施(SERC-FCF)的试验资料,对复式断面的垂向平均流速、床面剪切应力、达西—魏斯巴哈阻力系数和曼宁系数进行了分析。本文在查阅大量文献的基础上,总结了适用于计算复式断面过流能力的12种方法,其中包括6种经验法和6种理论分析法,通过这些方法的计算值与实测值的对比分析,得出了每种方法的计算精度。另外本文还介绍了用于水流数值模拟的HEC-RAS、CES和MIKE 21三种模型,并结合试验数据验证了这三种模型在复式断面水流运动研究中的适应性。本文所得的主要结论如下:(1)复式断面主槽部分的流速大,滩地部分的流速小,垂向平均流速在横向上存在流速梯度,尤其是在滩槽交界面处梯度最大;床面剪切应力的分布趋势与平均流速的分布相似,其变化规律与水深和滩槽过水面积之比有关;达西-魏斯巴哈阻力系数和曼宁系数的变化与床面条件、滩槽宽度比和水深都有一定的关系。(2)在12种复式断面过流能力的计算方法中,对角线分割法(DCM)、水平分割法(HDM)和Huthoff法(HCM)的计算精度都较高,可应用于复式断面的过流能力计算,而单一断面法的计算精度最差,因此不宜应用于复式断面过流能力的计算。由于Huthoff法具有一定的理论基础,所以该方法更具有普适性。(3)HEC-RAS的主槽部分计算值偏大,而滩地部分的计算值偏小;相比较HEC-RAS的计算结果,CES和MIKE 21的计算结果与实测值比较吻合,模拟效果较好,说明这两种数学模型可以应用于复式断面水流的研究。
[Abstract]:The natural channel is mostly duplex channel, and its cross section is usually composed of beach and main channel.In the dry season, the flow of water is mainly concentrated in the main channel of the river, and when the flood comes, the flow will overrun the channel beach and form the floodplain flow.Compared with a single section, the flow motion of the composite section is more complex.When the flow overruns, the interaction between the main channel and the two parts of the water body on the beach, the velocity distribution of the cross-section flow, the shear stress of the bed surface and the resistance will all change, and the formula for calculating the flow of a single section is no longer applicable.It is necessary to study a new method to describe the flow motion of a composite section, so it is of great significance to study the hydraulic characteristics of a composite section.Based on the experimental data of SERC-FCF, the vertical average velocity, bed shear stress, Darcy Weissbach resistance coefficient and Manning coefficient of the composite section are analyzed.On the basis of consulting a large number of literatures, this paper summarizes 12 methods suitable for calculating the overcurrent capacity of compound cross section, including 6 kinds of empirical methods and 6 kinds of theoretical analysis methods. Through the comparison and analysis between the calculated values and the measured values of these methods,The calculation accuracy of each method is obtained.In addition, three models, HEC-RASN CES and MIKE 21, which are used for numerical simulation of water flow, are introduced, and the adaptability of these three models in the study of the flow motion of complex cross-section is verified by combining the experimental data.The main conclusions obtained in this paper are as follows: (1) the velocity of the main channel of the composite section is large, the velocity of the beach is small, and the vertical average velocity of velocity exists in the transverse direction, especially at the interface of the beach and trough.The distribution trend of shear stress on bed surface is similar to that of average velocity, and its variation law is related to the depth of water and the ratio of water area of beach trough, and the change of resistance coefficient and Manning coefficient of Daxi-Weisbach coefficient is related to the bed condition.There is a certain relationship between the width ratio of beach and channel and the depth of water. (2) among the 12 methods for calculating the overcurrent capacity of composite cross section, the diagonal division method (DCM), the horizontal partition method (HDM) and the Huthoff method (HCM) have higher calculation accuracy, which can be applied to the calculation of the overcurrent capacity of the composite cross section.The calculation accuracy of single section method is the worst, so it is unsuitable to be applied to the calculation of overcurrent capacity of compound cross section.Because the Huthoff method has a certain theoretical foundation, the method is more general. The calculation value of the main slot part of HEC-RAS is larger than that of the beach part, and the calculated results of HEC-RAS and MIKE 21 are in good agreement with the measured values.The simulation results show that these two mathematical models can be applied to the study of complex cross section flow.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV133

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