While some may complain about Minnesota’s brutal winters, Jiarong Hong, PhD ’12, has made the state’s frigid weather a research ally. By observing how snow swirls around a spinning wind turbine, Hong has obtained the first-ever measurements of turbulent airflow around a utility-scale turbine.
Understanding how air interacts with wind turbines is crucial for lowering wind energy costs, explains Hong, an assistant professor of mechanical engineering at the University of Minnesota. Such insights would help make turbines more durable and efficient, and aid in the design of more productive wind farms.
Researchers have gleaned airflow knowledge via computer simulations and tests of few-meters-high model turbines inside laboratory wind tunnels. The tests involve injecting tracer particles such as oil droplets into the wind tunnels and tracking their flow using laser light and cameras.
But lab tests can’t capture on-the-ground reality. At more than 100 meters tall, commercial turbines are the size of skyscrapers. “At that scale, there is a significant difference in air flow dynamics,” Hong says.
He wanted to do particle-tracking tests on a full-scale turbine. The idea of using snow as a tracer came one evening as he watched snowflakes dancing around street lamps.
By shining a powerful searchlight beam onto a curved reflective surface during a nighttime storm, his team expanded the beam into a giant sheet that illuminated the snow particles around the turbine as it sliced through them. Photos and videos using high-resolution cameras gave Hong enough data to show how air behaves behind a utility-scale turbine. He published the results in June in Nature Communications.