High-Speed PIV Measurements of Transonic Shock-Buffet Control on a Supercritical Airfoil with Air-Jet Vortex Generators

This study investigates the control of transonic buffet instability over a two-dimensional OAT15A supercritical wing model using air-jet vortex generators (AJVGs). For this, high repetition rate particle image velocimetry (PIV) measurements were conducted in both the streamwise/wall-normal and streamwise/spanwise planes at 5 kHz in the Trisonic Wind Tunnel Munich under buffet conditions within the range 0.74 ≤ M∞ ≤ 0.76 and 4.5◦ ≤ α ≤ 5.5◦ . These measurements were conducted on an OAT15A wing model onto which a row of 37 AJVGs with a purely spanwise inclination of 45◦ was incorporated at 0.20c from the leading edge. The results show that the uncontrolled flow at M∞ = 0.755 and α = 4.5◦ exhibits a pronounced buffet mode at fb = 112.30 Hz ± 2.44 Hz (Stb = 0.068), characterised by large-amplitude shock motion and periodic growth and collapse of the downstream separated region. Under jet actuation at the same aerodynamic conditions, this instability is substantially mitigated, with the mean shock position shifting downstream by up to 0.091c (measured at a chord-normal distance of ŷ = 0.10c), and the standard deviation of the shock motion decreasing by approximately 68% with respect to the uncontrolled baseline case. A spectral analysis of shock motion also reveals a reduction of nearly 98% in the power spectral density associated with the dominant buffet mode. Furthermore, statistical analysis of the reverse-flow region demonstrates a strong suppression of large-scale separation events and with corresponding increased likelihood of small/diminishing reverse flow regions. Analysis based on Spectral POD further affirms the attenuation of the dominant buffet mode. Parametric investigations across multiple jet-injection pressures and aerodynamic conditions show that AJVG actuation consistently stabilises the interaction and suppresses buffet without introducing major disturbances into the outer flow.