本文選題：大擴(kuò)散角明渠段 + 水流特性　； 參考：《華北水利水電大學(xué)》2017年碩士論文

【摘要】：在實(shí)際工程中,受限于場(chǎng)地不足,在洞、渠結(jié)合部往往無(wú)法布置足夠長(zhǎng)的明渠擴(kuò)散過(guò)渡段,不得不采用大擴(kuò)散角的擴(kuò)散段來(lái)實(shí)現(xiàn)水流銜接。但是在此類(lèi)的擴(kuò)散段中,由于受邊界條件影響,水流在擴(kuò)散段中擴(kuò)散不充分,導(dǎo)致斷面能量分布不均,邊界層分離,在經(jīng)過(guò)擴(kuò)散段時(shí)水流會(huì)出現(xiàn)主流偏移的現(xiàn)象,形成大范圍的回流區(qū)及漩渦。這種不良流態(tài)會(huì)影響渠道的正常運(yùn)用,極大地限制了輸水明渠擴(kuò)散段的使用條件;為了要實(shí)現(xiàn)擴(kuò)散段的水流平順均衡過(guò)渡,必須了解其水流特性并相應(yīng)采取有效的調(diào)控措施。本文試圖通過(guò)系列水力模擬進(jìn)行擴(kuò)散段水流特性及調(diào)控措施的試驗(yàn)研究,主要借助兩個(gè)擴(kuò)散段水槽模型,研究隨流量和擴(kuò)散角改變,水流經(jīng)過(guò)擴(kuò)散段時(shí)的水力要素變化特征;根據(jù)大擴(kuò)散角明渠的水力特性提出用以調(diào)控水流的構(gòu)筑物形式,驗(yàn)證并優(yōu)化潛沒(méi)式三角翼體的調(diào)控效果。在明渠擴(kuò)散段無(wú)調(diào)控措施情況下,測(cè)量了擴(kuò)散段特征斷面水深、流速等水力要素,通過(guò)施放示蹤劑觀測(cè)了擴(kuò)散段及其連接段的水流流態(tài);分析研究了擴(kuò)散段水力要素的空間分布特性,擴(kuò)散段內(nèi)的邊界層分離情況,水流經(jīng)過(guò)擴(kuò)散段的能量損失,以及邊界條件改變對(duì)擴(kuò)散段及其連接段水流流態(tài)的影響。研究發(fā)現(xiàn)當(dāng)擴(kuò)散段擴(kuò)散角在大于8°時(shí),水流產(chǎn)生邊界層分離所形成的回流、漩渦相對(duì)較小,但水流穩(wěn)定性較差,主流易產(chǎn)生隨機(jī)性偏移現(xiàn)象。隨著擴(kuò)散角的加大,水流形成回流漩渦的范圍及強(qiáng)度亦增大,擴(kuò)散段特征斷面流速分布越發(fā)不均勻,能量損失增加,過(guò)流能力降低。當(dāng)擴(kuò)散角增大到45°時(shí),擴(kuò)散段兩側(cè)的回流區(qū)產(chǎn)生較強(qiáng)的剪切擠壓作用抑制水流橫向擴(kuò)散,也抑制主流的隨機(jī)偏移,水流非穩(wěn)定性又受到一定抑制。明渠擴(kuò)散水流下游斷面的過(guò)流條件與擴(kuò)散段水流狀態(tài)有一定的響應(yīng)關(guān)系,改變下游斷面過(guò)流條件,擴(kuò)散段主流的偏移狀態(tài)及下游連接段回流區(qū)的形態(tài)也隨之改變。根據(jù)大擴(kuò)散角情況下明渠水流特性,采取底部介入式調(diào)控水流方法,提出了一種適用于調(diào)控大擴(kuò)散角水流流態(tài)的潛沒(méi)式三角翼體,研究了該措施的導(dǎo)流機(jī)理。試驗(yàn)表明,三角翼體通過(guò)前端攻角對(duì)水流的分流與兩側(cè)翼板的導(dǎo)流作用,強(qiáng)化水流橫向擴(kuò)散運(yùn)動(dòng),改善了水流動(dòng)量的橫向分布形態(tài),增強(qiáng)了擴(kuò)散段水流結(jié)構(gòu)的穩(wěn)定性,使水流經(jīng)過(guò)擴(kuò)散段時(shí)能夠較為均勻地?cái)U(kuò)散到整個(gè)過(guò)流斷面,擴(kuò)散段及其連接段流態(tài)得到改善。
[Abstract]:In the actual engineering, limited by the shortage of the site, in the tunnel, the junction of the canal often can not arrange a long enough open channel diffusion transition section, so the diffusion section with a large diffusion angle has to be used to achieve water flow connection. However, in this kind of diffusion section, due to the influence of boundary conditions, the diffusion of water in the diffusion section is not sufficient, which leads to the uneven distribution of cross-section energy, the separation of boundary layer, and the phenomenon of mainstream migration when the flow passes through the diffusion section. Form a wide range of backflow zones and whirlpools. This kind of bad flow state will affect the normal operation of the channel and greatly limit the use conditions of the diffusion section of the open channel, in order to realize the smooth and balanced transition of the flow in the diffusion section, it is necessary to understand its flow characteristics and take effective control measures accordingly. In this paper, a series of hydraulic simulation is used to study the flow characteristics and control measures of the diffusion section, mainly by means of two flume models of the diffusion section, to study the characteristics of the hydraulic factors changing with the change of the flow rate and the diffusion angle, and when the flow passes through the diffusion section. According to the hydraulic characteristics of the open channel with large diffusion angle, the structure form used to control the flow of water was put forward to verify and optimize the control effect of the submerged delta wing. In the case of no control measures in the open channel diffusion section, the hydraulic factors such as water depth and velocity of the characteristic section of the diffusion section are measured, and the flow patterns of the diffusion section and its connecting section are observed by the application of tracer. The spatial distribution characteristics of hydraulic elements in diffusion section, the separation of boundary layer in diffusion section, the energy loss of water flow through diffusion section, and the influence of the change of boundary conditions on the water flow state of diffusion section and its connection section are analyzed and studied. It is found that when the diffusion angle of the diffusion section is greater than 8 擄, the reflux formed by the separation of the boundary layer is produced. The swirl is relatively small, but the stability of the flow is poor, and the main stream is prone to the phenomenon of random migration. With the increase of diffusion angle, the range and intensity of reflux vortex are increased, the velocity distribution of the characteristic section of diffusion section is more and more uneven, the energy loss increases, and the overcurrent capacity decreases. When the diffusion angle is increased to 45 擄, a strong shearing and squeezing action is produced in the circumfluence zone on both sides of the diffusion section to restrain the lateral diffusion of the flow and the random migration of the main stream, and the instability of the flow is restrained to a certain extent. There is a certain response relationship between the cross flow condition of the downstream section of the open channel diffusion flow and the flow state of the diffusion section. When the flow condition of the downstream section is changed, the migration state of the main stream of the diffusion section and the form of the backflow zone of the downstream connecting section also change. According to the characteristics of open channel flow under the condition of large diffusion angle, a submersible delta wing body suitable for regulating the flow state of large diffusive angle water flow is proposed by adopting the method of bottom interventional control. The mechanism of this method is studied. The experimental results show that the delta wing body distributes the water flow through the angle of attack at the front end, strengthens the lateral diffusion movement of the water flow, improves the transverse distribution of the water flow momentum, and enhances the stability of the water flow structure in the diffusion section. When the flow passes through the diffusion section, the flow pattern of the diffusion section and its connection section can be improved.
【學(xué)位授予單位】：華北水利水電大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TV133

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