ID 12

Spray Droplet Wake Transport Modeling

 

Abstract:

A relatively simple model (AGDISP) that describes the transport of droplets sprayed from a boom through the machine wake and then through the atmosphere to the point of deposition on a surface has been widely used over the past 25 years in the analysis and regulation of pesticide spraying. The original AGDISP model was applicable to aerial spraying and modeled the aircraft wake as two point vortices and prop wash or rotor wash in the case of helicopters. This technique has proven robust when compared to data, however, rapidly advancing modeling tools, higher expectations for modeling results in terms of accuracy and modeling domain, rapidly changing technology in the fields of chemical detection and application machinery all challenge this modeling approach. Modeling expectations now require that these models address long range drift of tiny amounts of spray, the intermittency of the atmospheric boundary layer that is enhanced by introduction of a porous plant canopy, temperature structure effects (stability) of the atmosphere, on-the-fly manipulation of spray systems, designer chemicals and adjuvants and many other technical issues. Two relatively recent sets of spray trials were conducted in challenging plant canopies to specifically evaluate some of the model limitations in highly turbulent, non-uniform scenarios. These trials and the implications will be discussed in detail.