A Fast Analysis of Pesticide Spray Dispersion by an Agricultural Aircraft Very near the Ground

This study provides a fast analysis of pesticide spray trails and dispersion influenced by crosswind, headwind, velocity field and the wake of an agricultural aircraft approaching the ground, to improve operational efficiency and reduce environmental impact. The lifting line-wingtip vortices mixture model is proposed to calculate induced velocity field around a monoplane far to 190 wingspans downstream, and N-vortex system based on point vortex dynamics is applied to simulate vortex rebound and vortex motion on considering extreme ground effect. The droplet trajectories governed by wake vortices and their induced velocity field are therefore determined under the Lagrangian framework. According to the ground deposition of typical droplets, the Gaussian mixture model is employed to predict droplet drift or dispersal for the whole spectrum of droplets in the spanwise direction. The fast analysis is compared to AGDISP and computational fluid dynamics (CFD) simulation for Thrush 510G aircraft, which runs on a common personal computer (CPU 2 GHz, memory 2 GB) within 3.2 s, faster than AGDISP and CFD, and does not rely on swath width input needed by AGDISP. The results suggest crosswind speed and droplet size are two leading factors affecting the drift and ground deposition. To increase droplet size or reduce the portion of fine droplets, the pesticide drift can be suppressed in some degrees.