小型植保无人机下洗气流场影响雾滴运动特性规律研究

Investigation of Effects of Downwash Airflow Field on Droplet MotionCharacteristics of Small Plant Protection Unmanned Aerial Vehicles

为了研究小型无人机下洗气流场对雾滴运动特性的影响规律,以小型无人机为基础,采用Navier-Stokes(N-S)方程、realizable k-ε模型和Semi-Implicit Method for Pressure-Linked Equations算法,对施药过程中的下洗气流场和雾滴离散运动进行了详细的数值模拟分析。研究分析无人机下洗气流的速度特性、雾滴沉积特性以及作业高度对农药沉积效果的影响。通过试验结果可知,模拟值与试验值的相对误差在20%以内,验证了下洗气流场数值模型的可行性。进一步模拟分析结果表明,在无人机喷药平台的影响下,下洗气流场在距离旋翼1 m处达到速度峰值。随着作业高度的增加,雾滴逐渐分散并扩散。雾滴主要分布在两个“气流引入区”和两个“气流导出区”,该分布特征有助于优化施药效果和提高农药的使用效率。根据分析结果,当无人机飞行作业姿态与地表保持平行,且将作业高度调整至0.8~1.0 m之间时,可显著提高农药沉积量,从而提高植保无人机的施药效果。本研究验证了下洗气流场数值模型的可行性,为小型植保无人机的对靶雾滴漂移及沉积研究提供了参考依据。

In an effort to investigate the influence of downwash airflow field on droplet motion characteristics of small unmanned aerial vehicles(UAVs)and enhance pesticide application efficiency,small UAVs were utilized as the basis and the Navier-Stokes(N-S)equations,realizable k-εmodel,and Semi-Implicit Method for Pressure-Linked Equations algorithm were employed to detailed numerical simulations of the downwash airflow field and droplet dispersion motion during the spray process were carried out.The primary research focus encompassed the analysis of velocity characteristics of the UAV downwash airflow,droplet deposition characteristics,and the impact of operating height on pesticide deposition.By comparing simulated values with measured values,it was confirmed that the relative error between the simulation and the experiment remained within 20%,thereby verifying the feasibility of the downwash airflow field numerical model.Further simulation analysis results indicated that,under the influence of the UAV spray platform,the downwash airflow field attained its peak velocity at a distance of 1 m from the rotor.With the increase in operating height,the droplets gradually dispersed and diffused.The droplets were primarily distributed in two“airflow introduction zones”and two“airflow export zones”,which contributed to further optimization of spraying effects and enhanced efficiency of pesticide utilization.In light of the analysis results,it was substantiated that when the UAV flight operation attitude was kept flush with the ground and the operating height was adjusted to 0.8~1.0 m,pesticide deposition could be significantly increased,ultimately improving the pesticide application efficacy of plant protection UAVs.The research result verified the feasibility of the numerical model of downwash airflow field,and provided a reference for the study of the drift and deposition of target fog droplets based on small plant protection UAVs.