Abstract
Atmospheric stability can significantly influence the spray drift in aerial applications; however, to date its effects remain unclear. In this study, a large spatiotemporal aerial application simulation model was constructed using different atmospheric boundary layer (ABL) stabilities. Three sets of ABL stability conditions were considered: unstable, stable, and neutral. Velocity, temperature, turbulence kinetic energy, and turbulence dissipation rate were set in detail as boundary conditions. The simulation results indicated that, using a simulation of the typical fixed-wing agricultural aircraft operating at typical altitudes and speeds, the upwind vortex decays more slowly than the downwind vortex, while the movement of the downwind vortex is also faster. The strength of the vortex was found to influence the droplet concentration. Droplets dispersed more quickly under unstable conditions probably because of the turbulent kinetic energy were greater. Droplets under stable conditions moved much rapidly downwind but drifted at lower altitudes than under unstable conditions. The diameter of most of the drift spray droplets was <100 μm. The simulation results indicated that off-target deposition in the stable case was greater than in the unstable case by nearly 300% around at downwind distances of 100 m, 180 m, 700 m, and ∼200% at around 220 m and 550 m. Therefore, unstable atmospheric conditions, which are most likely to occur from 06:00 and 19:00 during a day appear to be a better choice for reducing drift losses. The simulation results are expected to help improve the comprehensive understanding of aerial application drift and to assist in choosing appropriate times and conditions to perform such operations. • Aerial spraying of pesticides is studied considering atmospheric boundary layer. • Vorticity field, droplet movement at various atmospheric stabilities are simulated. • Results show vortex shape and decay rate are affected by atmospheric stabilities. • Spraying operations in unstable weather conditions enable wide distribution. • Spraying operations in stable conditions result in more off-target deposition.
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