穿河管道周围流场及冲刷特性试验研究
发布时间:2018-01-22 02:41
本文关键词: 管道冲刷 三维流场 漩涡 冲刷深度 模型试验 出处:《沈阳农业大学》2017年硕士论文 论文类型:学位论文
【摘要】:随着运输行业的不断发展,管道运输在输水、输气、输油、供电等方面给人们生活带来了极大的便利。然而,近年来水下管道破坏问题并没有得到很好解决。管道一旦损坏不仅会给带来经济损失,还会人们的生活带来不便,甚至引起一系列环境污染问题。目前国内外有关于管道冲刷方面的研究不是很多,而直接能应用于实践的研究成果更稀少,故亟需加快对穿河管道冲刷方面的研究。本研究的主要目的是通过物理模型试验的方法了解管道周围流场特性及冲刷特点,为管道穿越工程设计提供科学依据。同时,通过本次研究也可以丰富管道与河流的冲刷机理,促进泥沙运动理论的进一步发展。本次研究采用定床模型试验和动床模型试验相结合的方法,利用超声多普勒流速仪测量管道周围三维流速,研究管道模型周围流场及冲刷规律。本次试验共设置12组工况条件,其中动床模型试验和定床模型试验各6组。通过对定床模型试验和动床模型试验结果的对比分析,可以总结出以下规律:(1)横管在不同工况下尾迹漩涡宽度基本保持在1.2~1.5倍直径范围内,并在大漩涡的产生过程中伴有小漩涡不断形成、消失的现象;而立管尾迹漩涡随傅汝德数增大而变窄,当傅汝德数在0.104~0.393之间时,尾迹漩涡宽度在1.2~2.0倍直径范围内。(2)水流在流经管道模型前纵向流速减小而垂向流速增大,横管最大流速在中层管后位置,而立管最大流速出现在管道两侧。管道模型周围紊动强度和雷诺应力都随流速的增大而增大,立管在各工况下底层、中层、表层流速、紊动强度和雷诺应力分布规律基本一致,而横管中层紊动强度和雷诺应力最大,流速变化最大。(3)从水平推力、动水浮力和净水平推力随流速变化规律的曲线图可以看出净水平推力增长的最快,而动水浮力增长的最慢。(4)当管前水流流速小于模型沙起动流速时,管道基本不会产生局部冲刷。当管前水流流速大于模型沙起动流速时,半埋状态下最先发生冲刷的位置是横管前约0.5倍直径处,而立管两侧位置最先发生冲刷。(5)在同一来流条件下,横管的局部冲刷深度要大于立管,这是由于横管周围紊动强度大于立管。横管半埋在模型沙中时,流速越大,管道从半埋至完全裸露历时越短。立管冲刷过程前期冲刷速度比较快,当局部冲刷停止时达到最大冲刷深度。(6)从冲刷坑平面形态看,立管周围冲刷坑的范围随流速的增大而增大;而横管冲刷坑范围基本不变,在顺水流方向上宽度约为三倍管径大小。
[Abstract]:With the continuous development of transportation industry, pipeline transportation in water, gas, oil, power supply and other aspects of people's lives has brought great convenience. In recent years, the problem of underwater pipeline damage has not been solved very well. Once the pipeline is damaged, it will not only bring economic loss, but also bring inconvenience to people's life. Even cause a series of environmental pollution problems. At present, there are not a lot of research on pipeline erosion at home and abroad, and the research results that can be directly applied in practice are more rare. The main purpose of this study is to understand the characteristics of the flow field and scour around the pipeline by physical model test. It provides scientific basis for pipeline crossing engineering design. At the same time, through this study, it can enrich the erosion mechanism of pipeline and river. To promote the further development of the theory of sediment movement. In this study, the method of fixed bed model test and moving bed model test was used to measure the three-dimensional velocity around the pipeline by ultrasonic Doppler velocimeter. The flow field and scour law around the pipeline model were studied. Twelve working conditions were set up in this experiment. There were 6 groups of moving bed model test and fixed bed model test respectively. The results of fixed bed model test and moving bed model test were compared and analyzed. It can be concluded that the following rule: 1: 1) the wake vortex width of the transverse tube under different working conditions is basically kept in the range of 1.5 times the diameter of the wake, and in the process of the formation of the maelstrom, the small swirl is formed continuously. The phenomenon of disappearance; The wake vortex of the riser becomes narrow with the increase of the Fourier number, when the Fourier number is between 0.104 and 0.393. The wake vortex width is within the range of 1.2 ~ 2.0 times diameter.) the longitudinal velocity decreases while the vertical velocity increases before the flow through the pipe model, and the maximum velocity of the transverse tube is located behind the middle tube. The maximum flow velocity of the riser appears on both sides of the pipeline. The turbulence intensity and Reynolds stress around the pipe model increase with the increase of the velocity. The turbulent intensity and Reynolds stress distribution are basically the same, while the turbulent intensity and Reynolds stress in the middle layer of the transverse tube are the largest, and the velocity variation is the largest. The curve of dynamic water buoyancy and net horizontal thrust with the change of velocity can be seen that the net horizontal thrust increases fastest, but the slowest of dynamic water buoyancy increase. 4) when the flow velocity in front of the pipe is less than that of the model sand starting velocity. When the flow velocity in front of the pipe is larger than the starting velocity of the model sand, the first scour in the semi-buried state is about 0.5 times the diameter of the transverse pipe. Under the same flow condition, the local scour depth of the horizontal tube is greater than that of the riser, which is because the turbulence intensity around the horizontal tube is greater than that of the riser, and the transverse tube is half buried in the model sand. The higher the velocity of flow, the shorter the duration of pipeline from half-buried to completely exposed. The earlier scour speed of riser scour process is faster, when the local scour stops, the maximum scour depth is reached. 6) from the plane shape of scour pit. The range of the scour pit around the riser increases with the increase of velocity. However, the range of the horizontal pipe scour pit is almost unchanged, and the width is about three times the diameter of the pipe in the direction of the water flow.
【学位授予单位】:沈阳农业大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:U171
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