As wind energy production expands around the world, engineers have identified a nagging problem: When a wind turbine spins, its blades create disturbances in the air that can reduce the amount of energy produced.

This turbulence, or "wake," can cut a wind farm's power output by 10 to 20 percent. But assessing the particulars of the problem has been difficult. Computer simulations and wind tunnels have helped, but it's difficult to see the phenomenon on a large, commercial-scale turbine in the real world because minute changes in air patterns are invisible to the naked eye.

Now, researchers at the University of Minnesota have hit upon a novel solution: To see how a utility-scale wind turbine chops into the surrounding air, watch it