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Three-dimensional imaging system for analyses of dynamic droplet impaction and deposition formation on leaves

X. Dong, H. Zhu, X. Yang
Transactions of the ASABE 2013 v.56 no.5 pp. 1641-1651
digital images, droplets, image analysis, leaves, quantitative analysis, spray deposition, video cameras
A system was developed to assess the dynamic processes of droplet impact, rebound and retention on leaf surfaces with three-dimensional (3-D) images. The system components consisted of a uniform-size droplet generator, two high speed digital video cameras, a constant speed track, a leaf holder, and light sources. The droplet generator produced uniform droplets of 100 to 800 µm. The video cameras captured droplet impact images from two different angle views for 3-D droplet impaction analyses. The speed of cameras to capture images was up to 50,000 frames per second with image resolution up to 1,280×800 pixels. The speed track was used to mount and drove the droplet generator at constant speeds ranging from 1.6 to 10 km/h-1. The leaf holder supported leaves at various orientations and distances from the droplet generator. Waxy and hairy leaves and water solutions amended with a non-ionic surfactant were used to verify the system functions. Five motion processes of droplets after they impacted on waxy and hairy leaf surfaces were observed: complete retention, split retention, slide retention, splash and rebound. The droplet motion and deposition process before and after impaction were quantitatively analyzed with a 3-D image program. In conclusion, the imaging system was able to precisely observe and quantitatively analyze droplet impaction and deposition formation on hairy or waxy leaves when droplet diameter, droplet discharge speed, droplet discharge height, nozzle travel speed, leaf surface orientation, and spray formulation were variables.