本文選題：數(shù)值模擬　切入點：分流比　出處：《沈陽農(nóng)業(yè)大學》2017年碩士論文　論文類型：學位論文

【摘要】：分汊型河道是天然河道中最為常見的一種形式,目前在分汊口或者分支下游應用攔水建筑物來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。不同的來流流量、支流與干流不同的分汊角度、不同的攔河堰位置、不同的攔河堰高程、分汊口不同攔河堰長度等都會改變河道內(nèi)的水流特性。附近用水常常從河道西支取水,合理布置西支攔水建筑物對合理利用西支至關(guān)重要,所以本文數(shù)值計算分析的水流特性,對分汊河道取水具有重要意義。本文采用應用淺水方程、空間離散和時間積分的Mike21 FM軟件對丹東愛河炮臺頂段進行數(shù)值模擬,計算區(qū)域范圍是從丹東愛河大橋到東支下游900m,干流到東支河段長2.7km,西支河段長1km。并利用丹東愛河物模試驗結(jié)果來驗證數(shù)模模擬計算的準確性,將模型調(diào)試合適之后增加計算的邊界變量和工況,對影響分汊河道水流特性的來水流量、分汊角度和攔河堰進行多組對比計算,計算天然河道不同來流流量、不同分汊角度和不同攔河堰的河道分流比、流場和主流線的變化等。主要得出以下結(jié)論:(1)天然河道不同流量水流特性數(shù)值分析分汊型天然河道隨著流量的增大西支分流比依次遞增,斜率越來越小。隨著流量的增大,回流區(qū)淤積面積在增大,有效過流寬度減小,泄流能力減小,對兩岸堤腳流速比較敏感。從主流線變化中還看出分汊型天然河道流量越小主流線偏移程度越大,驗證了"大水取直,小水坐彎"的水流形態(tài)。(2)不同分汊角度河道水流特性數(shù)值分析隨著分汊角度的增加西支分流比依次遞減,隨著分汊角增加變化斜率變大。通過流場分析可知當河道分汊角度小于等于50°時,流場回流區(qū)變化不大,大于50°時回流區(qū)呈線性下降,分汊角對河道左岸堤腳流速的影響不明顯,右岸堤腳流速隨著分汊角的增加而增大。分汊角度在40°～50°之間對兩岸的沖刷較小。(3)西支不同攔河堰位置河道的水流特性數(shù)值分析通過丹東愛河西支的不同位置布置攔河堰來分析越靠近上游的攔河堰的分流比越小,西支X0+400～X0+550之間分流比變化比較穩(wěn)定。左右岸寬度增加的比較緩慢,隨著寬度的增加,斷面有效過流寬度在減小,攔河堰在上游更有利于泄洪,攔河堰堰頂流速都比較大,在堰后50m左右都會有流速驟降的現(xiàn)象。水流主流線經(jīng)過攔河堰后都向河道左岸偏移,所以應對堰后左岸加強防護。(4)西支不同攔河堰高程河道的水流特性數(shù)值分析在水流的分流比中可知東西支分流比與堰頂高程呈線性關(guān)系,可以根據(jù)西支的需求用內(nèi)插的方法找出理想的堰頂高程。隨著堰頂?shù)脑黾?回流區(qū)寬度越小,有效過流寬度越大,且左右岸堤腳流速變化趨勢相同,攔河堰的高程不影響主流線。(5)分汊口不同攔河堰長度的河道水流特性數(shù)值分析攔河堰長度越長西支分流比越大,對下游過流量有影響,對回流區(qū)寬度沒有影響,不影響河道的有效過水寬度。左岸堤腳流速隨著攔河堰長度的增加出現(xiàn)的越早,右岸流速最大值出現(xiàn)在同一點,最大值依次增大。分汊口處攔河堰長度對分汊口處的主流線影響較大,長度越長主流線越靠近河道中心線,長度越短偏離的越大。
[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.

【學位授予單位】：沈陽農(nóng)業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TV133

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本文編號：1645295