An LES Investigation of the Separated Flow Past An Airfoil at High Angle of Attack

Abstract

An investigation of the separated flow past an unswept wing (NACA-4415 airfoil) at high angle of attack ($\alpha$ = 18{\textdegree}) was carried out based on large-eddy simulations. As a first step a relatively low chord Reynolds number of Rec= 20, 000 was chosen yielding a leading-edge stall. The flow field in this range of $\alpha$ and Recis dominated by asymmetric vortex shedding with a Strouhal number St{\textasciiacutex} ≈ 0.2. A strong vortex develops almost periodically in the vicinity of the trailing edge. The life cycle of this vortex structure is controlling the flow field. At the leeward side of the airfoil a large clockwise rotating recirculation region of nearly constant pressure exists. A periodically occurring shedding motion of this vortical structure into the wake is not observed. The entire flow field is very similar to the previously investigated flow past an inclined flat plate.