Influence of periodically varying incident velocity on the application of semi-empirical dynamic stall models

Abstract

The dynamic stall behavior of an OA209 rotorcraft airfoil is examined under the influence of a varying incident velocity. Therefore, a harmonic flowvelocity variation is added to the pitch motion of the airfoil in antiphase. Results from twodimensional unsteadyRANScomputations are presented for steady and periodic flow velocity. The unsteady flow velocity in the computational domain is generated by a fore-aft motion of the airfoil. Both methods are approximations of the flowconditions a blade section of a helicopter rotor experiences during fast forward flight. Finally, the numerical predicted aerodynamic coefficients are used to investigate the modeling capabilities of semi-empirical formulations for a simultaneous angle of attack and incident velocity change.