Vortex formation and shedding from an airfoil at high angle of attack: a numerical study

摘要

The investigation is concerned with separated turbulent flows past a flat plate and an unswept wing at high angles of attack. For both configurations large-eddy simulations were carried out. First, a relatively low Reynolds number Re_c = 20,000 was chosen yielding a leading-edge stall. The flow is dominated by asymmetric vortex shedding predefined by strong vortices developing almost periodically in the vicinity of the trailing edge. The life cycle of these structures is controlling the entire flow field. At the leeward side of the airfoil and the plate, a large clockwise rotating recirculation region of nearly constant pressure exists. In the second step, the Reynolds number of the airfoil flow was increased to Re_c = 100,000 leading to a completely different flow behavior including a laminar separation bubble, transition behind the bubble, and separation of the turbulent boundary layer at about 70% chord length. Asymmetric vortex shedding as observed before is not found.