# Whats Going Around Wind Turbines: Turbulent Vortices.

I am researching how wind flows behind wind turbines by analyzing experimental and numerical data. The experimental data has been collected around the turbine that is pictured below; and the numerical model is based on this turbine.

I have made most of my current research progress by using a colleague’s numerical simulation that estimates wind velocity around a wind turbine. I am examining how tip vortices change across time and space. One specific investigation concerns the merging of two adjacent vortices. Since corotational vortices attract each other, the tip vortices sometimes merge together. To quantify this process, I am measuring the distances between adjacent vortices and the areas of those vortices. I hypothesize that by graphing the ratio of their distance to their area as they move downstream, I will find distinct phases in the merging process. I believe that when this ratio of distance to area decreases below a certain level, they will accelerate towards each other much more quickly.

A two dimensional slice of a numerical simulation is depicted below. The color shows the vorticity magnitude; the downstream direction is right, and the ground is located about 100 m below the x axis. The top of the turbine blades would be located on the lower left; here you can see distinct circular tip vortices in red. Farther downstream, the vortices appear to interact, as the vorticity in between the vortices is higher than it is upstream.

The image below depicts how these vortices merge into a vortex sheet. This vortex sheet does not always develop, for it depends on the amount of incoming turbulence and on the ratio of the wind speed to the turbine’s rotational velocity. The color scheme has been changed since the last image to emphasize the merging process.

While I work in Minneapolis, MN, I live in St. Paul. I am staying with 5 Macalester College students. The rent is great: \$200/month for the best room in the house (it has great big windows). This is my first time living in a college house, and I like it; for there are usually people around to talk to. I enjoy the camaraderie of the house. The Twin Cities have been very nice. Minneapolis’s culture is a lot like Portland’s. Everyday, I take 6 miles of fabulous biking trails to work. This is a tiring, yet rewarding, ride. When it rains, I use the cities’ good public transportation system. I have gone to fun, free events, including a museum, a jazz festival, a hip hop/spoken word festival, a bike race, a play, fireworks, and a swimming lake. I have been thinking about living here in the future, but the cold winters and the mosquito-infested summers might keep me away. I have, however, successfully fought off the mosquitoes; and I am thoroughly enjoying my time.