Mechanism and Reynolds Number Dependence of Shock-Induced Buffet on Transonic Airfoils

Summary

Tests were carried out at transonic speeds to investigate the effect of the Reynolds number on the buffet process. In these tests the airfoil model investigated was equipped with regular pressure orifices, dynamic pressure transducers and surface hot-film sensors. The unsteady flow field was observed by high-speed real-time holographic interferometry. The analysis of the results revealed that within the domain of heavy buffet the shock oscillation frequency decreased with increasing Reynolds number — in accordance with the effect of viscosity on the extent of the shock-induced separation bubble at steady conditions — while prior to buffet onset the shock oscillation frequency increased with Reynolds number. The investigation will be continued with the Reynolds number variation eventually being carried up to full-scale conditions.