Scaling Relationships Volumetric Size Distributions in Flat Fan Sprays of Agricultural Tank Mixes

In the application of pesticides via sprays, the volumetric droplet size distribution (VDSD) influences the efficacy of the application as well as the risk of off-target spray deposition. However, VDSD prediction is complicated in agrochemical sprays because the nozzles employed have unique, complex geometries, and because of the influence that active herbicides and adjuvants have on the properties of the spray. We have utilized conservation of energy arguments to develop a scaling relationship to predict VDSDs from flat fan sprays of agricultural tank mixes, and experimentally tested this relationship using laser diffraction interferometry for agriculturally relevant tank mixtures, including active pesticides and both emulsion-forming and rheology-modifying drift control adjuvants, sprayed with complex geometry, flat fan nozzles typical of field application. Specifically, for 9 nozzle-tank mix combinations and across multiple nozzle sizes, we show that VDSDs can be normalized by the Sauter mean diameter (), and normalized distributions collapse for given nozzle type-spray tank mix combination. We also show that the Sauter mean diameter normalized by the nozzle hydraulic diameter () scales with the ratio of product of tank mix surface tension and hydraulic diameter divided by the nozzle pressure drop, with a scaling exponent of 1/3.