DYNAMIC STALL ANALYSIS OF S809 PITCHING AIRFOIL IN UNSTEADY FREE STREAM VELOCITY

In this paper, the dynamic stall of S809 airfoil that widely used in horizontal axis wind turbine, in different reduced frequencies is investigated. The simulation was carried out numerically handling Navier-Stokes equations. For this purpose, the segregated solver with SIMPLE algorithm was chosen to solve the momentum equations. The effect of turbulence on the flow field is taken into account using Shear Stress Transport (SST) kappa-omega turbulence model. The obtained numerical results are compared with experimental and a few numerical results. The results indicate that the kappa-omega SST model is in good agreement with experimental results for both steady and unsteady conditions. Furthermore, a non dimensional parameter, relating the acceleration of unsteady free stream velocity and acceleration of pitch motion (known as reduced frequency), is also investigated. In addition, the results show that any increase in the reduced frequency increases the instantaneous aerodynamic characteristics of oscillating airfoil.