设有栏河堰的分汊型河道水流特性数值分析

发布时间：2018-03-21 19:50

本文选题：数值模拟　切入点：分流比　出处：《沈阳农业大学》2017年硕士论文　论文类型：学位论文

【摘要】：分汊型河道是天然河道中最为常见的一种形式,目前在分汊口或者分支下游应用拦水建筑物来合理利用分支水量的事例很多,但是天然河道水流特性的研究不是很多。不同的来流流量、支流与干流不同的分汊角度、不同的拦河堰位置、不同的拦河堰高程、分汊口不同拦河堰长度等都会改变河道内的水流特性。附近用水常常从河道西支取水,合理布置西支拦水建筑物对合理利用西支至关重要,所以本文数值计算分析的水流特性,对分汊河道取水具有重要意义。本文采用应用浅水方程、空间离散和时间积分的Mike21 FM软件对丹东爱河炮台顶段进行数值模拟,计算区域范围是从丹东爱河大桥到东支下游900m,干流到东支河段长2.7km,西支河段长1km。并利用丹东爱河物模试验结果来验证数模模拟计算的准确性,将模型调试合适之后增加计算的边界变量和工况,对影响分汊河道水流特性的来水流量、分汊角度和拦河堰进行多组对比计算,计算天然河道不同来流流量、不同分汊角度和不同拦河堰的河道分流比、流场和主流线的变化等。主要得出以下结论:(1)天然河道不同流量水流特性数值分析分汊型天然河道随着流量的增大西支分流比依次递增,斜率越来越小。随着流量的增大,回流区淤积面积在增大,有效过流宽度减小,泄流能力减小,对两岸堤脚流速比较敏感。从主流线变化中还看出分汊型天然河道流量越小主流线偏移程度越大,验证了"大水取直,小水坐弯"的水流形态。(2)不同分汊角度河道水流特性数值分析随着分汊角度的增加西支分流比依次递减,随着分汊角增加变化斜率变大。通过流场分析可知当河道分汊角度小于等于50°时,流场回流区变化不大,大于50°时回流区呈线性下降,分汊角对河道左岸堤脚流速的影响不明显,右岸堤脚流速随着分汊角的增加而增大。分汊角度在40°～50°之间对两岸的冲刷较小。(3)西支不同拦河堰位置河道的水流特性数值分析通过丹东爱河西支的不同位置布置拦河堰来分析越靠近上游的拦河堰的分流比越小,西支X0+400～X0+550之间分流比变化比较稳定。左右岸宽度增加的比较缓慢,随着宽度的增加,断面有效过流宽度在减小,拦河堰在上游更有利于泄洪,拦河堰堰顶流速都比较大,在堰后50m左右都会有流速骤降的现象。水流主流线经过拦河堰后都向河道左岸偏移,所以应对堰后左岸加强防护。(4)西支不同拦河堰高程河道的水流特性数值分析在水流的分流比中可知东西支分流比与堰顶高程呈线性关系,可以根据西支的需求用内插的方法找出理想的堰顶高程。随着堰顶的增加,回流区宽度越小,有效过流宽度越大,且左右岸堤脚流速变化趋势相同,拦河堰的高程不影响主流线。(5)分汊口不同拦河堰长度的河道水流特性数值分析拦河堰长度越长西支分流比越大,对下游过流量有影响,对回流区宽度没有影响,不影响河道的有效过水宽度。左岸堤脚流速随着拦河堰长度的增加出现的越早,右岸流速最大值出现在同一点,最大值依次增大。分汊口处拦河堰长度对分汊口处的主流线影响较大,长度越长主流线越靠近河道中心线,长度越短偏离的越大。
[Abstract]:Braided river is the most common form of natural river, at present in the bifurcated mouth or branch of downstream applications of buildings to the rational use of water retaining water branch of many examples, but the research on the flow characteristics of the natural river. Not many different inlet flow rate, stem flow and tributary river branch angle is different, different the weir position, different weir height, branching and different weir length will change the flow characteristics of the river water from the river nearby. Often the West Branch of water, reasonable arrangement of the West Branch of the water retaining building is important to the rational use of the West Branch, so the flow characteristics of the numerical calculation and analysis. Has an important significance on braided river water. The application of shallow water equations, numerical simulation is carried out in Dandong Fort top spatial discretization and time integration of Mike21 FM software, the calculation range is from the bridge in Dandong To the East Branch of the East branch to the downstream 900m river length is 2.7km and the West Branch of the river long 1km. and use the result in Dandong model to verify the accuracy of numerical simulation calculation, the model debugging right after increasing boundary condition calculation variables and the water flow impact on the flow characteristics of braided channel, braided angle and weir were calculated and compared. The calculation of natural river flow to different, different angles and different braided distributary channel weir flow ratio, and the mainstream line changes. We draw the following conclusions: (1) analysis of braided river along with the increase of flow rate increases the diversion ratio of West Branch numerical flow characteristics of different flow in natural river, slope is more and more small. With the increase of flow rate, the recirculation zone in the silted area increases, the effective width decreases, the discharge capacity decreases, more sensitive to both sides by means of change from the mainstream line velocity. Also see the anabranched natural river flow less mainstream line offset a greater degree of validation of the flood direct, flow patterns of small water sitting bent ". (2) numerical flow characteristics of different branch angle increased with the anabranched River on the West Branch of the angle of the split ratio is decreasing, with branching angle increases changes in the slope becomes larger. The flow field analysis when the anabranched channel angle is less than or equal to 50 degrees, the flow recirculation zone changes little more than 50 degrees when the recirculation zone decreased linearly and the influence of branching angle on foot on the left bank of the river flow is not obvious, right foot velocity increases with the increase of branching angle of branch angle. Between 40 and 50 degrees of erosion on both sides of the smaller. (3) the West Branch of the flow characteristics of different weir River numerical analysis by Dandong in the West Branch of the weir located closer to the upstream of the weir flow ratio is small, the West branch of X0+40 Between 0 ~ X0+550 is more stable than shunt changes. The increase of the width of the left and right bank is relatively slow, with the increase of the width, effective flow width decreases, the weir in the upstream is more conducive to the flood, the weir crest velocity is relatively large, at about 50m after weir will flow suddenly drop phenomenon. The main flow line passes through the weir after all to offset on the left bank of the river, so we should strengthen the protection of the left bank after weir. (4) in the analysis of water diversion ratio in the East branch and Gao Cheng weir flow ratio has a linear relationship with the West Branch of the flow characteristics of different weir Gao Cheng River numerical method based on Gao Cheng in the top the West Branch needs interpolation find the ideal weir. With the increase of weir, the recirculation zone width is smaller, the effective width is larger, and the left and right bank dike flow the same trend, Gao Cheng weir did not affect the mainstream line. (5) channel and different length of weir Numerical river flow characteristics analysis of weir length of the West Branch of the split ratio is larger, has influence on the downstream flow, has no effect on the width of recirculation zone, the effective width of water does not affect the river. The left foot velocity with weir length increases appear more early, the flow velocity of the maximum value appears in the same point, the maximum value increases. Branch outlet weir length of the mainstream line branching in the mouth of the impact is bigger, the longer the length of the mainstream line closer to the centerline of the river, the shorter the length deviation is greater.

【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】：TV133

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