单旋翼植保无人机翼尖涡流对雾滴飘移的影响

Influence of Wing Tip Vortex on Drift of Single Rotor Plant Protection Unmanned Aerial Vehicle

为研究单旋翼植保无人机翼尖涡流对雾滴飘移的影响特性,基于格子玻尔兹曼(Lattice-Boltzman,LBM)方法的自适应细化物理模型,对单旋翼无人机的旋翼流场进行了数值模拟。通过改变无人机喷杆的垂直距离和喷头在旋翼下方的位置,研究了不同飞行速度下,无人机翼尖涡流对雾滴飘移的影响规律。为捕获到不同粒径的雾滴在无人机下洗流场中的运动轨迹,采用基于拉格朗日离散相粒子跟踪法模拟了雾滴的运动轨迹。为验证数值模拟的准确性,进行了试验验证,研究结果表明:当无人机飞行速度大于3 m/s时,机身后方开始出现螺旋型尾涡,且飞行速度越大、飞行高度越高,尾涡向机身后方的扩散距离越远;当飞行速度为5 m/s、飞行高度为3 m时,38%的雾滴因螺旋尾涡而造成空中飘移,其中粒径小于100μm的雾滴约占总飘移雾滴数的80%;喷杆距离主旋翼的高度对雾滴因翼尖涡流造成的飘移影响不明显,但喷头的位置越靠近主旋翼的边缘,雾滴越容易被翼尖涡流卷吸。

Plant protection drone has great application prospects in agricultural production due to its low working height,flexible operation,good adaptability to terrain,slight environmental pollution and high efficiency in pest control. However,it could cause secondary disasters with droplets drift due to wingtip vortices. To investigate the effect of wing tip vortex flow of a single-rotor unmanned aerial vehicle on droplet drift, the flow field under a single-rotor unmanned aerial vehicle（UAV） was simulated numerically based on an adaptive thinned physical model of the lattice-Boltzman（LBM） method. The drift characteristics at different flight speeds of the wingtip vortex were examined for various nozzle positions and vertical distances between different spray booms. The Lagrange discrete particle tracking method was applied to capture accurately the trajectories of droplets with different particle diameters.Spray tests were conducted to verify the accuracy of the numerical simulation. It was shown that as the UAV flight speed was greater than 3 m/s,a spiral tail vortex appeared at the rear of the fuselage. The range of the tail vortex behind the fuselage became longer as the flight speed or flight altitude got higher.And 38% of the droplets was drifted by the spiral tail vortex at the flight speed of 5 m/s and the flight height of 3 m,in which 80% of the drifted droplets was smaller than 100 μm. The distance between the sprayer and the main rotor had little effect on the drop drift caused by the wingtip vortex. While thenozzle was closer to the edge of the main rotor,the droplets can be more easily sucked by the wingtip vortex.