Characterization of transonic shock oscillations over the span of an OAT15A profile

Abstract

The flow over a wing model with aspect ratio 2 and based on the supercritical airfoil (OAT15A) was experimentally investigated for a fixed Reynolds number (Re_textrm{c}) of 3times 10^{6} and numerous aerodynamic conditions. The angle of attack (AOA) and the Mach number (M_mathrm {infty }) were varied between 5^{circ } and 6.5^{circ }, and between 0.72 and 0.75, respectively. Here we focused on the dynamics of the shock front at incipient and developed buffet conditions, by employing background-oriented schlieren measurements on the wing’s upper surface. The spanwise variations of the shock front statistics and its frequency content were examined. The shock oscillations appeared to be the superposition of multiple fluid modes, of which the most dominant was the classic 2-D buffet, which induced uniform chordwise oscillations of the shock front. The hypothesis was formulated that the remaining modes are linked to physical phenomena reported in the literature, namely the side-wall boundary layer and the vortices detected in the mid-span separated flow.