The development and extension of mathematical models from first principles regarding the breakup of liquid sheets into droplets has been proposed almost 50 years ago but only recently has theoretical work been undertaken to understand this phenomenon. A two-phase (oil-in-water) continuous sheet of fluid emanating from a spray nozzle breaks into drops is first initiated by forming holes within the sheet. The formation of holes is what begins the breakup mechanism for a variety of different formulation types. Various models describing hole growth (once formed) and collision to form cylindrical ligaments, where these ligaments break into droplets via the well-known Rayleigh-Plateau stability theory. What is lacking is a hole perforation model to begin this atomization process that accounts for hole formation within a continuous sheet of sprayed fluid. In addition, a refinement in the breakup of cylindrical ligaments into drops via the Rayleigh-Plateau stability criteria now accounts for both primary and satellite drop formation. The modeling tool (written in Python) is used to recover experimental observations of the breakup of two-phase sheets from agricultural nozzles, beginning with nucleation of holes that form in these fluid sheets to ultimately obtain the atomization droplet size of interest (e.g., reduction of drops &lt; 150 microns). This work focuses on the nucleation of holes (where, why and how) and follows previous endeavors in this area using Agent Based Modeling (Rajan and Cryer, 2019). Once nucleation of holes within the sheet is adequately quantified (goal of this work), then all the fundamental modeling pieces are in place to simulate the spray behavior for the next generation of two-phase formulations to achieve low drift potential [i.e., nucleation of holes, hole growth and collision to form ligaments, followed by ligament breakup into drops]. Several examples for drop formation beginning with nucleation of holes in two phase liquid sheets following optimization are provided, and excellent agreement with observations is found (especially for formulations containing large oil drop sizes). Current refinement (both mechanistic and empirical) for the mechanisms of oil-in-water atomization are planned in 2021, along with investigations into Suspension Concentrate (SC), and mixtures of SC plus Capsule Suspensions (CS) formulations to learn about how nucleation methods outlined in this document can be amenable to other formulation types.

Optimizing multi-phase heuristic model of agrochemical spray drift

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.