Using a Minnesota blizzard as a visualization tool, researchers at the University of Minnesota (UMN; Minneapolis, MN) have mapped the airflow around large wind turbines -- information essential to understanding how wind turbines interact with one another in wind "farms."1
As wind turbines have grown to more than 100 m tall, field research in real-world settings has become more difficult.
"In the lab, we use tracer particles to measure airflows of wind turbine models in wind tunnels, but our research was extremely constrained by an inability to measure flows at the large scale," said Jiarong Hong, a UMN mechanical-engineering assistant professor and lead researcher on the study. "Most researchers thought measurements of this kind at the real-world scale were impossible."
36-m-wide light sheet
The research was done on a 2.5 MW wind turbine at the U.S. Department of Energy-funded Eolos Wind Energy Research Center run by UMN. A large searchlight with custom reflecting optics generated a 2D light sheet next to the 130-m-tall wind turbine for illuminating the snow particles in a 36-m-wide by 36-m-high area.
Videos taken of the snow vortices were digitized and synchronized with wake flow and load data from the fully instrumented research wind turbine. The technique was able to characterize the turbulence and air-velocity fields around the wind turbine. In particular, blade-generated coherent motions such as blade-tip and trailing sheet vortices could be matched with their instability mechanisms; such information will be important in determining spacing and geometry of turbine placement in future wind farms.
1. Jiarong Hong et al., Nature Communications (2014); doi: 10.1038/ncomms5216