PIV Measurements of Buffet with Artificial Noise

The transonic buffet flow field around supercritical airfoils is dominated by self-sustained shock wave oscillations on the suction side of the wing. Current theories assume that this unsteadiness is driven by a feedback loop of disturbances in the flow field downstream of the shock wave of which the upstream propagating part is formed by acoustic waves. The present experimental study aims at analyzing the impact of acoustic disturbances on the shock wave movement during buffet. Therefore, the buffet flow field around a supercritical DRA 2303 airfoil model is influenced with artificial sound waves introduced downstream of the airfoil by a loudspeaker. The flow conditions are defined by the Mach number \(M_{\infty } = 0.73\), the Reynolds number range based on the chord length of \(1.8 \times 10^6 \le Re_{c} \le 1.95 \times 10^6\), and the angle of attack of \(\alpha = 3.5^{\circ }\). High-speed particle-image velocimetry measurements are performed in the shock wave region. The results reveal that the unsteady flow field varies with the high-frequency pressure disturbances and their amplitude modulation. These data are considered as preliminary results which will serve for further studies concerning the investigation of buffet onset.