Stochastic modelling of turbulent spray dispersion in the near-field of orchard sprayers

A Lagrangian approach is adopted to study the turbulent dispersion of spray droplets in the near-field of air-assisted orchard sprayers. In order to compute the mean and turbulent properties of the air flow generated by the moving sprayer, the generalised mass and momentum conservation equations, coupled with a k-epsilon turbulence model, are solved numerically using finite volume methodology. These equations utilise a spatial-averaged porous medium model to take into account the effect of interactions between the air flow and crop. Airborne spray flux distributions have been calculated from ensemble-averaged particle trajectories predicted by two random-walk models (i.e. with and without temporal correlation). The results show that both stochastic models give reasonable agreement with measured drift profiles. (C) 1998 Elsevier Science Ltd. All rights reserved.