Flow Diagnostics of Transonic Shock Buffet Phenomenon of a Supercritical Airfoil using Dynamic Mode Decomposition

The complex interactions between shock waves and boundary layer is very commonly encountered on transonic aircraft wings. Within the very narrow regime of transonic flow at some particular Mach numbers and moderate angles-of-attacks some airfoil/wing configurations experience self-sustained shock oscillations that induces large aerodynamic load variations. Such oscillations, referred to as transonic shock buffet, can reduce flight handling qualities and structural integrity, and thereby limit aircraft flight envelopes. In this study, different types of shock phenomena on OAT15A supercritical airfoil has been analyzed using Dynamic Mode Decomposition. A dominant mode pair is identified to the same frequency as the buffet frequency is responsible for the shock position and oscillation of the boundary layer. Moreover, considerable number of higher order modes are identified as an integer multiple of the buffet frequency. Furthermore, the higher order modes show comparatively thinner coherent structures at the shock travel region as the mode order goes up.