Simulation of spray dispersal and deposition from a forestry airblast sprayer - Part II: Droplet trajectory model

FLUENT (TM), a commercial software package for computational fluid dynamics simulation, was evaluated for application in modeling the trajectories and deposition characteristics of spray droplets from a forestry airblast spra yer The Algonquin airblast sprayer uses a centrifugal blower which produces a mean axial air velocity of 30 m/s from a 20.3 cm diameter round outlet l ocated 3 m above the ground. An assembly of three cone nozzles is arranged vertically at the outlet. An experiment with water and Rhodamine tracer dye was conducted in a shelterwood site To determine droplet deposition. Krome kote (TM) card targets were placed within and outside of a canopy of poplar saplings along a spray sampling line perpendicular to the line of travel o f the sprayer Ten sampling stations were located along the sampling line at 2 m intervals, from 3 to 21 m from the sprayer outlet. Measured and simula ted deposition data were generally in good agreement, but there, were discr epancies for smaller droplets (24 to 70 mum). FLUENT predicted that such dr oplets would be carried beyond 18 m from the sprayer outlet. However they w ere observed almost uniformly distributed on the targets along the sprayer swath in the region of 3 to 21 m from the sprayer: