Investigation of low Reynolds number flows over a dedicated wind turbine blade airfoil

Abstract

Finding a high lift and low drag airfoil has been remaining one of the fundamental design objectives for wind turbine blades. The performance of a high lift airfoil at high Reynolds (Re) number for large wind turbine blades is different from that at low Re number for small wind turbine blades. This paper investigates the performance of a dedicated high lift airfoil at high Re number in low Re number flows through wind tunnel testing and computational fluid dynamics (CFD) modelling. The airfoil section used in the research is the DU93-W-210 airfoil. The Shear Stress Transport (SST) k-ω fully turbulent model and the transition SST model were applied to investigate the aerodynamic performance of the airfoil. Good agreements were achieved between the experimental results and CFD analysis. Airfoil aerodynamic coefficients at different low Re numbers with different turbulence intensities were compared and analysed. The free stream turbulence intensity demonstrates apparent influence on prediction of aerodynamic coefficients using the transition SST model. Differences were observed for the maximum lift, minimum drag and stall angle at different Re numbers. The lift to drag ratio of the airfoil decreases dramatically at low Re number comparing to high Re number. The results indicate that full consideration of low Re numbers effects on aerodynamic performance is required in small wind turbine blade design.