Numerical Study of Transonic Buffet on SC(2)-0518 and OAT15A with Vortex Generators

Abstract

Predicting the transonic buffet and its onset is important for ascertaining the performance limits of an aircraft at its critical angle of attack. Additionally, a physical understanding of the buffet suppression technique is important for preventing shock wave oscillations. In this study, we conducted zonal detached-eddy simulations to numerically investigate the effects of vortex generators (VGs) on buffet suppression and to discuss the differing flow characteristics of the SC(2)-0518 and OAT15A supercritical airfoils when the chordwise position of the VGs is varied. The results for both airfoils equipped with VGs demonstrated significant suppression of large-scale lift oscillations across all calculation steps. VGs placed at 10% of the chord (10%c) from the leading edge produced higher time-averaged lift coefficients for both airfoils, with the OAT15A airfoil showing a particularly notable 2.5% improvement in lift coefficient, leading to a 0.82% increase in L/D ratio. The visualized results indicated that the interaction between the shock wave and VGs leads to variations in the separation point, depending on the VG chordwise position. This separation is affected by the aerodynamic characteristics of the airfoil shapes and the wake induced by the VGs, ultimately resulting in changes to the lift coefficient.