天然河道垂线流速分布类型及其影响因素初探

发布时间：2018-10-19 18:11

【摘要】：天然河道中的水流均为非恒定流,当前,河道非恒定问题日益突出。由于明渠非恒定流本身较为复杂,对明渠非恒定流的很多特性方面的研究一直未能有较大的突破。研究天然河道的垂线流速分布类型及其影响因素。对正确的掌握流速垂线分布规律及天然河流河床演变、水利学科的发展以及港口、航运及城市防洪等实际问题的解决,都有重要的理论和工程意义。为探讨天然河道的垂线流速分布类型,本文以室内ADV清水试验和长江螃蟹碛至冰盘碛水道实测资料为基础,分别研究其流速分布形态,对比找出主要影响因素。采用不同的计算公式对研究河段的推移质输沙率进行计算。通过对垂线流速分布和推移质输沙率、地形坡降和流量的关系探讨,进一步明确天然河道垂线分布的类型及其影响因素,得到主要研究结论如下:(1)通过室内ADV清水水槽试验,在没有外界因素的干扰下,清水非恒定流流速剖面为常规的“上大下小”型,其流速分布满足传统的对数分布。(2)以长江螃蟹碛至冰盘碛水道为研究对象,基于大量实测流速资料,天然河流的非常规流速分布可归纳总结为7种类型,分别为“3”型、“C”型、“1”型、“S”型、“7”型、“反S”型和“反C”型。(3)初步分析认为“7”型垂线流速多出现在地形陡升处。“1”型垂线流速多出现在河床洼地的中心处。“C”型垂线流速常出现于河道沿水流方向缩窄、洪峰陡涨以及挖槽和港池的出口等处。“反C”型垂线流速常出现在雍水水库的回水末端、河道沿水流方向展宽、河道洪水陡落、挖槽和港池进口等处。“S”型与“反S”型垂线流速多出现于河道近岸的有植被地带。(4)研究河段垂线流速分布形态绝大多数呈“3”形分布,此流速分布模式多出现在地形较平坦的河道主流区,由于长江河道宽阔,河道主流区流速不受两岸边壁及植被影响,初步分析认为天然河道水流的紊动性为该种分布模式形成的主要原因。(5)在垂线平均、最大流速和推移质输沙率的内在关系分析得出,研究河段垂线平均、最大流速和推移质输沙率变化情况具有良好的一致性,二者成严格的线性关系。(6)在垂线平均、最大流速和地形坡降的内在关系分析得出,研究河段垂线平均、最大流速和地形纵、横坡降变化情况具有较好的一致性。垂线平均流速与地形纵坡降成严格的二次函数关系,与地形横坡降的相关性较差。(7)分别将不同流量情况下的垂线平均流速和垂线最大流速进行对比分析可知,垂线平均流速和垂线最大流速均随着流量的增加而增大。各断面测点平均流速和最大流速增幅不一,初步分析认为,这是由于各断面形状不一以及各断面上下游地形变化导致。
[Abstract]:The flow in natural river is unsteady, and the unsteady problem is becoming more and more serious. Due to the complexity of the unsteady flow in the open channel, there has been no great breakthrough in the study of many characteristics of the unsteady flow in the open channel. The vertical velocity distribution of natural river and its influencing factors are studied. It is of great theoretical and engineering significance to correctly grasp the distribution law of velocity perpendicular to the evolution of natural river bed, the development of water conservancy discipline and the solution of practical problems such as port, shipping and urban flood control. In order to study the vertical velocity distribution type of natural river channel, based on the indoor ADV water test and the measured data of the Yangtze River crab moraine to glacial drift, the velocity distribution pattern of the river is studied, and the main influencing factors are found out. Different formulas are used to calculate the bed load transport rate of the studied reach. By discussing the relationship between vertical velocity distribution and bed load transport rate, topographic slope gradient and discharge, the types of perpendicular distribution of natural river and its influencing factors are further clarified. The main conclusions are as follows: (1) through indoor ADV clean water flume test, In the absence of external interference, the flow velocity profile of the unsteady flow in clear water is a conventional "upper, larger and lower" type, and its velocity distribution satisfies the traditional logarithmic distribution. (2) the Yangtze River crab moraine to glacial moraine channel is taken as the research object. Based on a large number of measured velocity data, the unconventional velocity distribution of natural rivers can be summarized into seven types, which are "3", "C", "1", "S", "7", respectively. (3) A preliminary analysis shows that the velocity of "7" vertical line appears in steep elevation of terrain, "1" type perpendicular velocity occurs mostly in the center of riverbed depression, and "C" type perpendicular velocity often occurs in river. The channel narrows along the direction of the current, Hong Feng rose sharply, as well as dredging and the outlet of the harbour pool and so on. The "anti-C" vertical velocity often appears at the end of the backwater in Yongshui Reservoir. The channel widens along the direction of the flow, and the river flood drops precipitously. The vertical velocity of "S" type and "anti-S" type are mostly found in the vegetated zone near the river channel. (4) the distribution of velocity distribution of vertical line in the river reaches is mostly "3" shape. The velocity distribution pattern mostly appears in the flat river channel mainstream area. Because the Yangtze River channel is wide, the flow velocity in the main river channel is not affected by the side wall and vegetation on both banks. The primary analysis shows that the turbulence of natural river flow is the main reason for the formation of the distribution model. (5) the relationship between the maximum velocity of velocity and the rate of bed load transport in the vertical line is analyzed. The results show that the average vertical line of the river reaches is studied. The variation of maximum velocity and bed load transport rate is in good agreement, and they are in strict linear relationship. (6) in the vertical line average, the relationship between maximum velocity and topographic gradient is analyzed, and the perpendicular average of the river reach is studied. The maximum velocity of flow and the variation of vertical and transverse slope have good consistency. The relationship between the average velocity of the vertical line and the vertical gradient of the terrain is strictly quadratic, and the correlation between the average velocity of the vertical line and the gradient of the vertical slope is poor. (7) the comparison and analysis of the average velocity of the vertical line and the maximum velocity of the vertical line under different flow rates are made. Both the average velocity of the vertical line and the maximum velocity of the vertical line increase with the increase of the flow rate. The average velocity and the maximum velocity increase of each section are different. The preliminary analysis shows that this is due to the different shape of each section and the topographic variation of the upper and lower reaches of each section.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV133

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