颗粒离散元和点球浸入边界法在泥沙输运研究中的应用

发布时间：2018-06-05 09:02

  本文选题：颗粒离散元 + 点球浸入边界法　； 参考：《天津大学》2014年硕士论文

【摘要】：泥沙颗粒在三维紊流场中的输移是典型两相流问题。本文采用基于有限体积法的高效能紊流并行计算程序——CgLES,结合点球浸入边界法和基于“事件驱动”模型和“弹簧—阻尼”模型的颗粒离散元法,对泥沙输移问题进行数值模拟研究,可以模拟百万甚至千万量级的泥沙颗粒运动,需要的计算资源较少,适合研究较大空间尺度的泥沙演变过程,更接近于工程应用,同时具有较高精度,对于泥沙颗粒的输移研究具有重要意义。本文应用上述方法对明渠紊流边界层中泥沙颗粒的运动与分布,明渠床面沙纹的演变以及直立桩柱周围的局部冲刷三种典型的泥沙输移问题进行了数值模拟。研究发现:明渠中颗粒的输运对紊流的统计特征有影响,其运动与近壁区紊流拟序结构密切相关。惯性颗粒在明渠紊流边界层中分布存在不均匀性,易聚集形成顺流向条带结构,这种不均匀性主要受St数的影响,当St≈O(1)时,不均匀性最为显著。明渠紊流中沙纹会发生合并,在沙纹数量不变的条件下,沙纹高度近似呈线性增长,而沙纹的长度的平均值却保持恒定。随着沙纹高度的增大,输沙率逐渐降低并趋于稳定。当沙纹发生合并时,沙纹的高度快速增加,输沙率也随之大幅降低。直立桩柱周围的局部冲刷首先发生在与展向对称面呈40°左右的桩柱两侧,此处的冲刷深度在整个冲刷过程中一直保持最大。随着冲刷发展,冲刷区域和淤积区域逐渐向下游延伸,冲淤变化速度减小,最终达到冲淤平衡。
[Abstract]:The transport of sediment particles in three-dimensional turbulent flow is a typical two-phase flow problem. In this paper, a parallel computation program of high efficiency turbulent flow based on finite volume method, CgLES, is adopted, and the particle discrete element method based on event-driven model and "spring-damping" model is combined with point-ball immersion boundary method. A numerical simulation study on sediment transport can simulate the movement of millions or even tens of millions of sediment particles, which requires less computing resources. It is suitable for studying the sediment evolution process on a large spatial scale and is closer to engineering application. At the same time, it has high precision, which is of great significance for the study of sediment transport. In this paper, the motion and distribution of sediment particles in turbulent boundary layer of open channel, the evolution of sand grain on open channel bed and the local scour around vertical pile column are numerically simulated. It is found that the transport of particles in the open channel has an effect on the statistical characteristics of turbulent flow, and its motion is closely related to the quasi-sequence structure of turbulent flow near the wall. The distribution of inertial particles in the turbulent boundary layer of open channel exists inhomogeneity, and it is easy to gather and form a stripe structure along the direction of flow. This inhomogeneity is mainly affected by St number, and the inhomogeneity is the most obvious when St 鈮，

本文编号：1981438