基于CFD-DEM耦合的迷宫流道水沙运动数值模拟

基于颗粒动力学理论的欧拉-拉格朗日固液多相湍流模型,针对灌水器迷宫流道内水沙运动进行了CFDDEM耦合数值模拟研究,分析了迷宫流道内流体流场、单个沙粒的轨迹线、速度和沙粒群的运动规律、分布特性等。结果表明:沙粒在流道深度中心面附近分布较多,靠近边壁较少,随着流道深度减小,流道内沙粒的体积浓度成倍上升。流道深度越小,流道深度(Z方向上)水流运动速度越小,随着沙粒Z方向上运动速度增大,沙粒群穿过中心面次数越多,撞击边壁的次数越多,流道深度0.6 mm的撞击边壁次数是1.4 mm的7.01倍,边壁撞击次数的增加使沙粒高频率改变原有运动方向,增加了沙粒之间,沙粒与壁面之间的碰撞,该运动情况降低了沙粒运动速度,减少了动能,不利于沙粒通过迷宫流道,增加了堵塞几率。该方法可分析大量沙粒个体和群体运动,以及群体分布情况,从微观角度了解迷宫流道内沙粒运动,是迷宫流道结构设计的有效手段之一。

Numerical Simulation of Water and Sediment Flow in Labyrinth Channel Based on Coupled CFD-DEM

The depth of flow path of drip irrigation emitter is important geometrical parameter to anti-clogging performance. 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 with labyrinth channel. The trajectories and speed of single sediment, speed of sediment group, moving pattern and distribution of sediment group were analyzed. Simulation result indicated that the quantity of sand near the central plane of depth was more than that near the wall. The volume concentration of sediment in channel was increased several times with the decrease of depth. The depth was small;the speed of waterflow in depth direction was descended, but the speed of sediment in depth direction was risen. The average number of hit of each sediment was 14.31 when the depth was 0.6mm, but the number was 2.04 when the depth was 1.4 mm. The increase of impact frequency to wall changed original movement direction of sediment, augmented the number of times of collision between sands and between sand on the wall, which decreased velocity and kinetic energy, and it was difficult for sand to go through labyrinth channel, which caused clogging easily. This method was applied to analyze movement and distribution of sand individuality and group, learn the movement regular from micro-view perspective, and it had become an efficient technique in structure design of labyrinth channel.