Oscillatory control of shock-induced separation

An experimental investigation, aimed at delaying Bow separation as a result of the occurrence of a shock-wave/boundary-lager interaction, is reported. The experiment was performed using a NACA 0015 airfoil at high-Reynolds-nu mber incompressible and compressible flow conditions. The effects of Mach a nd Reynolds numbers were identified, using the capabilities of the cryogeni c-pressurized facility to maintain one parameter fixed and change the other . The main objectives of the experiment were to study the effects of period ic excitation on airfoil drag divergence and to alleviate the severe unstea diness associated with shock-induced separation (known as buffeting), Zero- mass-flux oscillatory blowing was introduced through a downstream directed slot located at 10% chord on the upper surface of the NACA 0015 airfoil. Th e effective frequencies generated 2-4 vortices over the separated region, r egardless of the Mach number. Even though the excitation was introduced ups tream of the shock wave, it had pronounced effects downstream of it. Wake d eficit (associated with drag) and unsteadiness (associated with buffeting) were reduced. The spectral content of the wake pressure fluctuations indica tes steadier how throughout the frequency range when excitation is applied. This is especially evident at low frequencies which are more likely to int eract with the airframe.