农药雾滴空间运行中的变形特征分析

以化学农药雾滴的空间运行过程为背景,构建了二维气液相界面追踪模型,通过COMSOL Multiphysics系统地研究了雾滴特征参数及风速等多因素耦合下单雾滴在横向风场中下落时的形变特征。结果表明,雾滴的形变会受黏性力、表面张力等内部因素和重力、曳力等外部因素的共同作用,外部作用力能够促进雾滴发生形变,而内部作用力阻碍雾滴的形变。雾滴的形变量随着雾滴尺寸和横向速度的增大而增大,随着动力黏度和表面张力的增大而减小;雾滴下落过程中的形变存在振荡周期,雾滴的形变周期随着雾滴尺寸的增大而增大,随着表面张力的增大而减小,但基本不受横向风速和动力黏度的影响。将雾滴的形变量、形变周期与韦伯数We、奥内佐格数Oh和雷诺数Re等量纲为1数进行拟合,可以预测雾滴的空间形变特性。研究结果对农药雾滴的空间飘移机理及其阻控技术的研发具有重要意义。

Deformation characteristics of chemical pesticide spray droplet during spatial motion

A two-dimensional gas-liquid interface tracking model coupled with level-set method is applied to simulate deformation process of chemical pesticide spray droplet. The effects of spray droplet diameter, surface tension, viscosity and air velocity are considered. It shows that spray droplet deformation is the result of comprise and competition between internal forces such as viscous force and surface tension, and external forces such as gravity and drag force. Gravity and drag force can promote droplet deformation, while viscous force and surface tension can hinder droplet deformation. The deformation of spray droplet can oscillate periodically during spatial motion and deformation characteristics of different spray droplets are investigated. The deformation amplitude can be enhanced by increasing spray droplet diameter and air velocity. Besides, it can be weakened by increasing the surface tension and viscosity of spray droplet. The deformation period can be prolonged by increasing droplet diameter and decreasing surface tension, but it is almost unrelated with air velocity and viscosity. Prediction models are proposed by dimensionless analysis to estimate deformation period and amplitude. The results can provide theoretical fundament for the development of spray drift reduction technology.