A System to Investigate 3-D Droplet Impact on Leaf Surfaces

A system was developed to investigate droplet dynamic impact and retention on leaf surfaces. The system consisted of a uniform droplet generator, two high speed digital video cameras, a constant speed track, a leaf holder, and a cool light source. The droplet generator produced mono-sized droplets ranging from 100 to 1,800 µm with a controllable speed. The video cameras were able to capture images at the speed of 40,000 frames per second with the resolution of 512×512 pixels. The track was used to mount and drive the droplet generator at a constant speed ranging from 1.6 to 10 km/h. The leaf holder could support leaves with different inclinations and distances from the droplet generator. With a commercially available 3-D image analytical software, the system was able to determine the dynamics of droplet impact, rebound and retention on hairy and waxy leaves when droplet diameter, droplet discharge speed, droplet discharge height, nozzle travel speed, leaf surface orientation, and spray formulation were the variables.