Project
Physics of spraying and droplet impact
In applications of pesticides, farmers typically spray liquids that include the active ingredient onto their fields. During spraying an aerosol is formed.
The air-borne droplets may drift away from their targets when the droplets are too small, or may fall off the leaves when the droplets are too large. The droplet size not only depends on technical details, such as the pressure applied to push the liquid through the nozzle, but also on formulation details.
Formulation science is well developed, but how a given formulation influences the droplet size in spaying applications, is much less well understood. Active ingredients are often formulated by using emulsions. In such products, there may also be surfactant- or polymer additives.
When the liquid leaves the nozzle, new water-air interface is formed. Emulsion droplets that are near the interface can coalesce with this newly formed interface. In this project there is a focus on the wettability of oil droplets at the air-water interface and how this correlates with the droplet-size distribution. Using an ultra-fast camera we can follow the droplet formation. The illustration shows examples of the breakup of the water film in a typical situation where a flat fan nozzle is used.
