Computational fluid dynamics investigation of some wind turbine rotor design parameters

This article presents an investigation of the relative importance of key design parameters of a horizontal axis wind turbine (HAWT) blade. Computational fluid dynamics (CFD) is used as the main tool, after validation against experimental data of the (National Aeronautics and Space Administration/National Renewable Energy Laboratory) NREL/NASA-Ames Phase VI wind tunnel campaign. Tip and root sections, blade aspect ratio, and pitch angle were analysed and all CFD calculations were performed using a compressible Reynolds-averaged Navier-Stokes solver. CFD grids of advanced multi-block topologies were used including up to 4.5 million cells. A grid convergence study indicated that a resolution of 3.4 million cells was adequate for the selected flow conditions, which correspond to an upwind wind turbine at 0 degrees yaw angle, 7 m/s wind speed, and 72 r/min rotational speed. Various root and tip configurations were considered and the results obtained indicate that the exact representation of the root and tip geometry of an HAWT has a small but finite effect in the thrust and torque levels at working conditions. This effect is however secondary to the effects of aspect ratio and blade pitch.