發(fā)布時間：2018-02-04 16:14

  本文關鍵詞： 階梯斜面 溢流壩 數值模擬 階梯消能工 流態(tài)　出處：《河北工程大學》2014年碩士論文　論文類型：學位論文

【摘要】：本文以Chinnarasri試驗數據為背景，通過數值模擬研究斜面階梯溢流壩的流態(tài)、摻氣和消能，主要研究內容有： 1）首先介紹了本文問題的研究背景，總結了階梯消能工應用的歷史背景、研究動態(tài)，列出近年來出現的幾種新型階梯消能工形式，重點總結了階梯消能工水流流態(tài)的分類、定義方法，總結摻氣點位置的研究現狀和摻氣機理的研究結果。給出數值模擬理論基礎，給出三的基本控制方程，介紹了數值模擬方法、離散方法和混合物模型的特點以及的使用條件、邊界條件類型和網格劃分方法。 2）本文應用標準k~ε模型進行數值模擬，采用水氣兩相流混合物模型（Mixture模型）模擬摻氣水流，采用四邊形非結構網格對模型進行網格劃分。壁面采用無滑移壁面邊界條件，進口邊界分別設水進口和空氣進口，壓力速度耦合采用PISO離散方法。 3）定義了水氣界面，對水平階梯和斜面階梯流態(tài)進行了模擬，得出水平階梯時，當hc/d=0.29時，為跌落水流；當hc/d增大至0.87時，為過渡流，隨著hc/d的繼續(xù)增大，水流變?yōu)榛兴鳎粚π泵骐A梯流態(tài)研究得出和水平面階梯基本相似的流態(tài)，即斜面階梯流態(tài)也出現跌落流、過渡流和滑行流三種情況，所不同的是在斜面階梯跌落流態(tài)下，沿壩面流程，依次出現貼壁水舌、跌落水舌和水氣漩渦三個階段，文中分析認為出現這種顯現的原因是階梯斜面對動能和勢能轉化影響造成的。研究發(fā)現，在滑行水流狀態(tài)下，斜面階梯傾角對水流流態(tài)影響不大。 4）對斜面階梯的摻氣特性進行了研究得出：沿壩面方向，階梯漩渦處水流摻氣濃度沿程呈增大趨勢，階梯邊角到水流表面之間斷面的摻氣濃度則沿程變化不大，在最末一階階梯上的摻氣濃度隨著傾角的增大略有減小，從溢流壩上游至下游的流程中，摻氣水深逐漸增大；摻氣濃度隨著來流流量的增大而減小，隨斜面階梯傾角的增大而增大，同時指出，斜面傾角的無限制增大可導致氣蝕現象的發(fā)生，，需進一步研究各壩坡下的最優(yōu)斜面傾角。 5）定義了消能率η的計算方法，對影響η的影響因素進行了理論分析，得出η和來流弗氏數F0，跌落系數FD，臨界水深hc和階梯高度d的比值hc/d，階梯斜面傾角θ以及階梯高度和長度的比值d/l有關。模擬研究了FD、hc/d和θ的變化對η的影響，得出η隨著FD和hc/d的增大而減小，隨著θ增大而增大，并對模擬數據進行擬合，得出FD~η、hc/d~η和θ~η之間經驗關系式，以及這些關系式的適用范圍。
[Abstract]:Based on the experimental data of Chinnarasri, the flow state, aeration and energy dissipation of stepped spillway dam with inclined plane are studied by numerical simulation in this paper. The main research contents are as follows: 1) firstly, the research background of this paper is introduced, the historical background of the application of stepped energy dissipators is summarized, the research trends are summarized, and several new types of ladder energy dissipators are listed in recent years. In this paper, the classification and definition method of step energy dissipator's water flow state are summarized, the research status of aeration point position and the research results of aeration mechanism are summarized. The theoretical foundation of numerical simulation and the basic governing equation of three are given. The numerical simulation method, the characteristics of discrete method and mixture model, the application conditions, the type of boundary conditions and the meshing method are introduced. 2) in this paper, the standard k- 蔚 model is used to simulate the aerated water flow, and the mixture model of water and gas two-phase flow is used to simulate the aerated water flow. A quadrilateral unstructured mesh is used to divide the model. The boundary condition of non-slip wall is adopted, the inlet boundary is set up with water inlet and air inlet, and the pressure and velocity coupling is performed by PISO discrete method. 3) the water / air interface is defined, and the horizontal and oblique staircase flow patterns are simulated. It is concluded that when the horizontal step is hc/d=0.29, it is a falling flow. When hc/d increases to 0. 87, it is a transitional flow. With the increase of hc/d, the flow becomes a sliding flow. The research on the gradient flow pattern of the inclined plane shows that the flow pattern is basically similar to that of the horizontal plane step, that is, there are also drop flow, transition flow and glide flow, which are different from those under the sloping ladder drop flow. Along the dam surface flow, there are three stages: sticking water tongue, falling water tongue and water vapor swirl. It is considered that the reason for this phenomenon is the influence of step slope on kinetic energy and potential energy transformation. Under the condition of sliding flow, the slope gradient angle has little effect on the water flow state. 4) the aeration characteristics of the inclined stepped are studied. It is concluded that along the dam surface, the aeration concentration of the flow is increasing along the direction of the dam surface. The aeration concentration of the cross section between the edge angle of step and the surface of the flow has little change along the course, and the aeration concentration on the last step of the first step decreases slightly with the increase of the inclination angle, from upstream to downstream of the overflow dam. The aeration water depth increases gradually; The aeration concentration decreases with the increase of the incoming flow rate and increases with the increase of the gradient angle of the inclined plane. At the same time, it is pointed out that the unlimited increase of the inclined angle can lead to the occurrence of cavitation erosion. It is necessary to further study the optimal slope dip angle under each dam slope. 5) the calculation method of energy dissipation rate 畏 is defined, and the influencing factors of 畏 are analyzed theoretically. The ratio of critical water depth (HC) to step height (d) is related to the ratio of the gradient angle 胃 and the ratio of the height of the step to the length of the step. The effects of the changes of the FDH / HC / d and 胃 on the 畏 are simulated. It is obtained that 畏 decreases with the increase of FD and hc/d, and increases with the increase of 胃. The empirical relationship between FD- 畏 hcrd畏 and 胃 畏 is obtained by fitting the simulated data. And the scope of application of these relations.
【學位授予單位】：河北工程大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TV653;TV135.2

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本文編號：1490604