Summer 2019

A mighty wind tunnel

College of Science and Engineering

Even the slightest breeze can create trouble for farmers spraying chemicals to control weeds, pests, and plant diseases in their fields. When a wind picks up droplets and carries them off, the crops may not get their full treatment. And if those substances drift into neighboring fields, they can potentially damage other crops or native vegetation. 

Researchers from the U’s College of Science and Engineering are partnering with WinField United, a wholly owned subsidy of Land O’Lakes, to more precisely target these substances. To make this work possible, WinField United donated a wind tunnel to the U for spray research. “Because of the donation, we have the most advanced low-speed agricultural spray wind tunnel in an academic setting,” says Chris Hogan, professor of mechanical engineering and principal investigator for the wind tunnel lab.

The tunnel and its dimensions. The top wind speed is 15 miles per hour. Three separate devices (right) measure particle size, velocity, and drift.
College of Science and Engineering

Making movies of droplets

The tunnel allows researchers to develop measurement techniques that are more precise and more informative. One is digital inline holography. The U’s Jiarong Hong, Benjamin Mayhugh Associate Professor and McKnight Land-Grant Professor, is using this technique to make 3D images of individual droplets, showing their size and shape and the way they move. The result is a “movie” that allows researchers to follow the droplets in three dimensions.

Image of droplets captured in 3D
Jiarong Hong

“There is no way we would have planned to do this research without WinField’s support,” Hogan explains. “It’s a really cool thing that’s happening at this university.”

Where the winds are blowing

In the future, Hogan sees spray researchers using image processing to develop ways to seek out and zap individual weeds. “We’ll go from using large sprayers to hunting and seeking,” Hogan says. “We’ll be able to use orders of magnitude less chemical, and there will be less risk for drift.”