An experimental investigation into the dynamic suitability of thick section aerofoils for the blades of large scale vertical axis wind turbines

The dynamic stall test facilities at Glasgow University has been enhanced to make it more productive and user friendly computer programs have been developed for the analysis and display of the data. The improvements have brought to light possible irregularities in some of the data collected, however, from the data set available, no final conclusions have been reached and a series of tests have been outlined to investigate these further. Five aerofoils were tested under various unsteady conditions which simulated those encountered by the blades of a vertical Axis Wind turbine with a swept area of 450m² (VAWT 450 at Carmarthen Bay). When the wind tunnel data was compared with measured data from VAWT 450 both sets were found to be in good agreement. Two dynamic stall models have been developed for the inclusion of dynamic stall into vertical axis wind turbine prediction codes. From these the following conclusions on the use of thick aerofoils for the blades of large scale vertical axis wind turbines have been reached:1. Once the angle-of-attack variation around the azimuth starts to exceed that required for static stall, increasing the frequency of rotation of the turbine, increases the aerodynamic efficiency of the blades.2. The higher the operating Reynolds number the thinner the aerofoil section that is required for maximum aerodynamic efficiency.