Hui Hu pulled a model wind turbine from the top of an office filing cabinet. The turbine tower was just 10 inches high. Its three blades were 10 inches in diameter. It was a perfect 1:320 scale reproduction of the 80-meter diameter wind turbines spinning across Iowa, the country's second-ranked state in installed wind power capacity. That mini turbine is helping a research team led by Hu, an Iowa State University associate professor of aerospace engineering, understand how hills, valleys and the placement of turbines affect the productivity of onshore wind farms.