Expansion of the USDA ARS Aerial Application spray atomization models

Authors: Fritz, Bradley - Brad; Hoffmann, Wesley; Martin, Daniel - Dan; Lan, Yubin

Submitted to: Proceedings Annual Conference on Liquid Atomization and Spray Systems
Publication Type: Proceedings
Publication Acceptance Date: 5/30/2011
Publication Date: 5/30/2011
Citation: Fritz, B.K., Hoffmann, W.C., Martin, D.E., Lan, Y. 2011. Expansion of the USDA ARS Aerial Application spray atomization models. Proceedings Annual Conference on Liquid Atomization and Spray Systems. Estoril, Portugal, September 5-7, 2011. p. 1-7.

Interpretive Summary: The USDA ARS aerial spray nozzle models are being updated using new, more accurate droplet sizing methods and techniques for a larger range of application airspeeds (up to 200 mph), reflecting the changing needs of aerial application industry. With these changes, there is a need to consolidate the older models, which were developed for limited ranges of nozzle orifice and airspeed, into single, unified models which cover the full range of airspeeds and nozzle settings. The unified models significantly reduce the amount of time and resources needed for development, which is desirable given the large number of spray nozzles and formulations for which models are needed by the industry. Because the current and updated models are created from datasets created by different laser diffraction instruments, there were some inherent differences, as previously documented by other researchers. Overall, the development of the unified models, combined with new methods of dissemination and improved user interfaces, will ultimately provide aerial applicators with a better toolkit for making critical operational decisions that result in more efficient and efficacious applications.

Technical Abstract: An effort is underway to update the USDA ARS aerial spray nozzle models using new droplet sizing instrumen-tation and measurement techniques. As part of this effort, the applicable maximum airspeed is being increased from 72 to 80 m/s to provide guidance to applicators when using new high speed aircraft. With this increase in applicable airspeed range and with a desire to consolidate a number of the older models, a method for unifying a number of partial range models (i.e. large and small orifice or airspeed models) into one unified model was examined. The new partial range models were compared to unified models, which were in turn compared to the presently used versions of the models for a flat fat and anvil deflection spray nozzle. There was a slight increase in the percent error in model predicted droplet sizes when comparing the new partial range models to the unified version, but the unified model with the greater range of applicable inputs significantly reduces the amount of time and resources needed in model generation, which is desirable considering the large number of spray nozzles and formulations for which models are needed by the industry. Since the current and updated models are created from different datasets created by different laser diffraction instruments, there are some inherent differences which have been observed in the past by other researchers. Further examination into the differences seen in the size classifications between the old and new models is needed better understand why they differ to the degree that they do. Overall, the development of the new models using the larger input ranges is supported but requires some additional understanding of the spray droplet size classification scheme. Combined with newer dissemination methods and improved user interfaces that are being developed, these models will ultimately provide aerial applicators with a better toolkit to use when making critical operational decisions that result in more efficient and efficacious applications.