滴灌灌水器迷宫流道结构对泥沙运动的影响

采用基于颗粒动力学理论的欧拉-拉格朗日固液多相湍流模型,选用夹角、上底宽、齿高、齿尖参差量、流道宽等五因素四水平组成16个迷宫流道模型,进行水沙运动CFD-DEM耦合数值模拟,分析沙粒群通过率、速度下降百分数、沙粒群运动和分布规律。结果表明:沙粒群通过率能有效描述迷宫流道的抗堵塞性能,沙粒群通过率与沙粒速度下降百分数呈负相关,沙粒群整体速度下降是影响迷宫流道内沙粒通过率的核心因素;沙粒速度的变化取决于流道内水流运动特性,而夹角、流道宽是影响水流特性的主要流道结构参数,其中夹角具有显著性影响;较优结构中可使沙粒始终受曳力牵引,大部分沙粒运行于主流区中,保持较高的运动速度,速度下降较小,动能损失少,通过率高,减少了被堵塞的机率;该方法统计了沙粒群运动及分布规律,从微观角度分析迷宫流道内沙粒运动,将有效提高迷宫流道结构设计效率。

Influence of Geometrical Parameters of Labyrinth Passage of Drip Irrigation Emitter on Sand Movement

In order to obtain the optimum geometrical parameters for improving the anti- clogging performance of labyrinth flow path of drip emitter,16 kinds of flow paths were designed according to the structural parameters such as angle, height, upper base, offset and width. An Eulerian-Lagrange liquid-solid multiphase turbulence model combined with the kinetic theory of granular flow was used to carry out simulation based on coupled CFD-DEM water-sand two-phase flow in drip irrigation emitter, which analyzed the pass rate of sand group, the percentage decrease in speed of sand, the movement and distribution regulars and force and so on. The result indicated that the clogging performance of labyrinth channel could be expressed by the pass rate of sand. There existed a negative relationship between the pass rate and percentage drop of sand group speed . The speed descending of sand movement was the key factor that affected the sand pass rate in labyrinth channel. The angle and width were the main structural parameters of flow passage that affected the water flow characteristics. The speed of sand particles depended on the flow characteristics of the flow channel, and the angle had a significant influence on sand speed. Sand was always drawn by drag force from water flow in the optimum structure. Most of the sand ran in the mainstream area, so they maintained high movement speed. Little sand lost kinetic energy, thereby it reduced the blocking probability. This method was applied to analyze movement and distribution of sand group, understand the movement of sand from micro-view perspective, and it had become an efficient technique in structural design of labyrinth channel.