【作者】 芮德繁；

【导师】 刘兴年；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2005， 硕士

【摘要】 天然河道都一般都可以概化为一系列弯段和直段的组合,因此对于理想弯道的水沙运动规律研究可以作为天然河道水沙运动规律研究的基础。传统的研究方法是采用相似准则下一定比尺的物理模型实验来研究,尽管物理模型实验具有自身的优点,但仍有许多不足之处。随着计算机技术的不断发展,数值模拟作为河流模拟领域一个重要手段,得到广泛的应用和发展。由于弯道特有的几何特征和边界条件,使得弯道中水流产生水面超高现象,从而在向心方向上产生压力差。在离心力和向心方向上的压力差作用下,弯道中水流将产生特有的运动方式,即弯道环流运动。就水流的整体而言,呈螺旋流运动。弯道环流的出现,从而引起弯道泥沙的横向输移,形成弯道凹岸冲刷、凸岸淤积的冲淤特性。对连续弯道而言,泥沙运动存在同岸输移和异岸输移两种。本文对弯道水流运动现象、泥沙的输移规律、床面剪切力的分布、弯道泥沙的起动和弯道输沙率等从理论上作了详细分析。在本文中,主要采用数值模拟和物理模型实验的方法,对弯道环流运动现象进行了模拟和测量,并分析环流运动对弯道泥沙输移的作用。本文采用了κ~ ε模型结合VOF 模型和Eulerian 两相流模型对连续弯道环流、弯道泥沙冲淤规律进行了数值模拟。以二维的水气两相流的VOF 模型结合雷诺时均法的κ~ ε双方程模型进行水气两相流计算,得到稳定流场作为三维水沙计算的初始进口条件。在连续弯道三维水沙计算中,采用结合雷诺时均法的κ~ ε双方程的Eulerian 两相流模型。在三维正交曲线坐标系下,建立描述水沙运动的控制方程,采用有限体积法离散方程,以SIMPLE 方法对压力场和速度场耦合计更多还原

【Abstract】 The natural channel can be seen composed by a series of bends and straight reaches. So, the study for the movement of water and sediment in the ideal bend can be seen as the basis in the natural channel. The traditional method is building a physical model in a certain scale and doing experiments. Though this method has many strongpoint of its own, but it still has many shortages. With the development of the computer technique, as one important method in the channel simulation field, it is applied and developed more and more. For the special boundary condition and geometry profile of meandering river, when water going into together with sediment, the former character will change, such as the superelevation of water surface and the difference of pressure in the centripetal direction. For these changes, the water in the meandering river will bring the movement of circulation. For the whole water, the special movement is the spiral flow. The sediment in the meandering will bring lateral moving because the transverse circulation. So the sediment of concave bank will be scoured and deposited in the convex bank. In the continuous meandering channel, the two different modes of sediment are the movement of same bank and different bank. In this paper, the movement phenomena of water, the transporation law of sediment, there is a particular discussion for the distribution of bed shear, the pick-up velocity of sediment and the sediment discharge in the meandering river. In this paper, the main method that is the numerical method and the experiment of physical model are used to simulate the circulation flow. After simulation, the effect by the circulation flow to the transporation of sediment is analysed in this paper. To choose the model suit for the simulation, many researching result of the former researches is discussed and used for reference in this paper, and at last the κ~ εmodel combined with VOF and Eulerian model is chose to do the numerical simulation work. At first, the velocity which is the outlet velocity of 2-D numerical model by using the VOF and κ~ εmodel is used as the inlet velocity of the 3-D numerical model. The control equations of 3-D water and sediment movement are described in the orthogonal curvilinear coordinates, and the equations is segregated by using the Finite Volume Method (FVM). The SIMPLE algorithm was adopted in the numerical program. For the control with the result of numerical simulation, the same size with numerical method model is used in the physical experiment. The result of physical experiment shows that the movement and evolvement of circulation flow accord with the result of numerical simulation. It is the same for the result of scouring and sedimentation.更多还原