CFD Studies of the Dynamic Stall Characteristics on a Rotating Airfoil

Abstract

The periodic changes of the angles of attack in time occurring in the Darrieus turbine blade result in the significant increase of unsteady characteristics, commonly referred as dynamic stall. CFD simulations using SST k-ω turbulence model with Kato-Launder correction were used to examine the physical phenomena occurring on the sectional airfoil of the blade. The blade was modeled as an airfoil rotating about its center of rotation. The CFD calculations show remarkable differences of the forces acting on the airfoil compared with the static condition due to the traveling vortices phenomena. The generation of leading edge and trailing edge vortices as the characteristics of dynamic stall was captured accurately. This provided more detailed information on the development of dynamic stall on the Darrieus turbine blade. The analysis of the stall event was obtained by considering the insertion flow occurring near the leading edge. The interactions of the travelling vortices in the upwind as well as in the downwind phases are presented in the present manuscript, providing deeper knowledge in the dynamic stall database of vertical axis wind turbines.