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Canopy Penetration by Aircraft Vortices

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131593439,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Milton E Teske, Harold W Thistle
Keywords:   AGDISP, aircraft vortices, canopy penetration, aerial spray.

Abstract. Over the last several years, USDA Forest Service modeling efforts have been directed toward refinement of canopy droplet capture in AGDISP. Approaches included exploring the behavior of the droplet trajectory through the canopy and the LAI characterization of the cross-sectional canopy structure, in addition to studying the effects of droplet bounce and shatter off plant surfaces. The dominant mechanism driving droplets into the canopy is the flow field generated by the aircraft vortices. While AGDISP damps these vortices by atmospheric turbulence, the model does not include the effect caused by scrubbing these vortices through the canopy. While early field work suggested that vortex scrubbing results in little change to the vortex circulation strength, it appears likely that this mechanism could slow droplet motion and enhance canopy capture. This paper examines the influence of canopy drag on vortical strength, based upon the use of an accepted atmospheric CFD code. It is expected that this work will improve the decay characteristics of aircraft vortices near and within a canopy, and help improve the modeling effort directed toward droplet deposition predictions.

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