Liquid sheet breakup and droplet evolution in agricultural sprays*

Spraying is a common process in everyday life with applications in agriculture, drug administration, printing, and painting. For agriculture purposes, small droplets are needed to enhance coverage of agricultural sprays, but not so small that they cause drift of the sprayed pesticides. Spray drift can cause the deposition of chemicals to undesired areas with a negative impact on livestock, ecosystems, and human health. In this work, different factors influencing spray breakup and droplet size distributions are discussed. Herein we experimentally measure the droplet size distribution of sprays from agricultural spray nozzles. The sprays were either homogeneous or contained an emulsion, and the dynamic surface and interfacial tensions were varied. We identified the influence on spray volume fraction below 150 μm and on the volume median diameter, which are correlated with the spray drift risk and deposition, respectively. The results of this work will help to understand the factors affecting a droplet size during a spraying process, towards increased efficacy of spraying pesticides.