A SIMPLIFIED HEAVY PARTICLE RANDOM-WALK MODEL FOR THE PREDICTION OF DRIFT FROM AGRICULTURAL SPRAYS

A simplified, two-dimensional random-walk model of particle dispersion that accounts for the crossing trajectories effect was proposed. The derived vertical particle velocity auto-correlation agreed adequately with the wind-tunnel measurements of Snyder and Lumley (1971, J. Fluid Mech. 48, 41-71). The dispersion predictions of the model were compared with field spraying experiments using a range of drop sizes. In general, the model agreed closely with the experimental evidence, but slightly over-estimated dispersion in the far-field region.