Contributed by the Solar Energy Division of the American Society of Mechanical Engineers for publication in the ASME JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received by the ASME Solar Energy Division, Jan. 2001; final revision, Jan. 2001. Associate Editor: D. Berg.

The National Renewable Energy Laboratory’s Unsteady Aerodynamics Experiment horizontal axis wind turbine installed in the NASA Ames 80 by 120 wind tunnel—the largest wind tunnel in the world. Note the person at the rail for scale.

Smoke can be emitted from the tip of the instrumented blade to aid in tracking the turbine’s wake expansion. Because the smoke becomes entrained in the tip vortex, it remains clearly visible far downwind of the rotor.

The 10 meter (33 feet) diameter turbine is capable of measuring the surface pressure on the instrumented (black) blade at 120 locations. In addition the 25 pressures in...

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