自动调流式滴头的内部流场数值模拟

Numerical Simulation of the Inner Flow Field for the Self-adjustment Flow of Drip Irrigation Emitter

根据自动调流式滴头的结构组成和工作原理,利用Auto CAD软件、计算流体动力学CFD技术的Fluent软件,建立由平角齿形消能流道和控制体形成滴头流量组合体的流体模型,并进行网格划分,分别以控制组合体的膜片开度0.5、1.0、1.5和2.0 mm为初始条件,以进口压力30、40和50 k Pa和壁面的粗糙高度、粗糙常数等为边界条件,采用SIMPLE算法的二阶迎风离散格式,对滴头的流量控制组合体进行水流运动通道内部流场的二维数值模拟,分析得出自动调流式滴头的平角齿形消能流道的速度矢量图、内部流场特征,在流道消能齿的单元处会产生独立的水流漩涡,容易引起灌溉水中杂质颗粒的累积、造成堵塞。为自动调流式滴头的结构优化改进、抗堵塞性和适宜工作压力取值范围提供了理论指导。

According to the structure composition and the working principle of the self-adjustment flow of drip irrigation emitter, the fluid model for controlling flow combination, which includes the straight tooth shaped flow channel and control flow form, is established by using the AutoCAD software and the CFD software of Fluent. Then the fluid models are respectively meshed with different diaphragm opening of 0. 5mm 1.5, 1.0, and 2.0 mm as the initial conditions, the pressure of water supply of 30, 40 and 50 kPa and the wall surface roughness height and roughness constant as the boundary conditions. Then the inner flow field of the control body with the straight tooth shaped flow channel in two dimensional for the adaptive drip irrigation emitter is numerically simulated by using the two order upwind discretization scheme of the SIMPLE algorithm. And the velocity profile and the characteristics of the internal flow field for emitter with the straight tooth shaped flow channel are analyzed. The results show that： the independent vortex flow can form at the unit of tooth channel, and easily causes the accumulation of impurities in irrigation water, resulting in blockage. The study can provide a theoretical guidance for structure optimization, improving anti-clogging and ensuring the proper working pressure range of the self-adjustment flow of drip irrigation emitter.