斜面阶梯数值模拟研究

发布时间：2018-02-04 16:14

本文关键词： 阶梯斜面溢流坝数值模拟阶梯消能工流态　出处：《河北工程大学》2014年硕士论文　论文类型：学位论文

【摘要】：本文以Chinnarasri试验数据为背景，通过数值模拟研究斜面阶梯溢流坝的流态、掺气和消能，主要研究内容有： 1）首先介绍了本文问题的研究背景，总结了阶梯消能工应用的历史背景、研究动态，列出近年来出现的几种新型阶梯消能工形式，重点总结了阶梯消能工水流流态的分类、定义方法，总结掺气点位置的研究现状和掺气机理的研究结果。给出数值模拟理论基础，给出三的基本控制方程，介绍了数值模拟方法、离散方法和混合物模型的特点以及的使用条件、边界条件类型和网格划分方法。 2）本文应用标准k~ε模型进行数值模拟，采用水气两相流混合物模型（Mixture模型）模拟掺气水流，采用四边形非结构网格对模型进行网格划分。壁面采用无滑移壁面边界条件，进口边界分别设水进口和空气进口，压力速度耦合采用PISO离散方法。 3）定义了水气界面，对水平阶梯和斜面阶梯流态进行了模拟，得出水平阶梯时，当hc/d=0.29时，为跌落水流；当hc/d增大至0.87时，为过渡流，随着hc/d的继续增大，水流变为滑行水流；对斜面阶梯流态研究得出和水平面阶梯基本相似的流态，即斜面阶梯流态也出现跌落流、过渡流和滑行流三种情况，所不同的是在斜面阶梯跌落流态下，沿坝面流程，依次出现贴壁水舌、跌落水舌和水气漩涡三个阶段，文中分析认为出现这种显现的原因是阶梯斜面对动能和势能转化影响造成的。研究发现，在滑行水流状态下，斜面阶梯倾角对水流流态影响不大。 4）对斜面阶梯的掺气特性进行了研究得出：沿坝面方向，阶梯漩涡处水流掺气浓度沿程呈增大趋势，阶梯边角到水流表面之间断面的掺气浓度则沿程变化不大，在最末一阶阶梯上的掺气浓度随着倾角的增大略有减小，从溢流坝上游至下游的流程中，掺气水深逐渐增大；掺气浓度随着来流流量的增大而减小，随斜面阶梯倾角的增大而增大，同时指出，斜面倾角的无限制增大可导致气蚀现象的发生，，需进一步研究各坝坡下的最优斜面倾角。 5）定义了消能率η的计算方法，对影响η的影响因素进行了理论分析，得出η和来流弗氏数F0，跌落系数FD，临界水深hc和阶梯高度d的比值hc/d，阶梯斜面倾角θ以及阶梯高度和长度的比值d/l有关。模拟研究了FD、hc/d和θ的变化对η的影响，得出η随着FD和hc/d的增大而减小，随着θ增大而增大，并对模拟数据进行拟合，得出FD~η、hc/d~η和θ~η之间经验关系式，以及这些关系式的适用范围。
[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.
【学位授予单位】：河北工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV653;TV135.2

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