Wind Tunnel and Numerical Study of a Small Vertical Axis Wind Turbine

This paper presents a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine. Wind tunnel tests were carried out to ascertain overall performance of the turbine and two and three dimensional unsteady CFD models were generated to help understand the aerodynamics of this performance. Wind tunnel performance results are presented for cases of different wind velocity, tip-speed ratio and solidity as well as rotor blade surface finish. It is shown experimentally that the surface roughness on the turbine rotor blades has a significant effect on performance. Below a critical wind speed the performance of the turbine is degraded and above it, the turbine performance is enhanced by a smooth rotor surface finish. A Significant increase in performance coefficient is observed for the high solidity rotors over most of hte operating range. Dynamic stall behavior and the resulting large and rapid changes in lift coefficient are shown to be the likely cause of changes to rotor pitch angle that occurred during early testing. This small change in pitch angle caused significant decreases in performance.