A Numerical Study on Aerodynamic Resonance Phenomena in Transonic Airfoil Flow

We present preliminary results from an ongoing numerical investigation of unsteady shock/boundary layer interaction on a 2-d supercritical airfoil in transonic flow. Initially, DLR's time accurate flow solver TAU is used to demonstrate the ability of standard URANS methods to predict self-sustained periodic shock oscillations well known as shock buffet. Next, emphasis is put on the fixed-point stability of the steady flow field below the shock buffet onset. Therefore we perturb the flow in time with small harmonic deflections of the airfoil geometry and random noise impulses. With increasing angle of attack the steady flow is shown to develop a damped aerodynamic resonance, that degenerates finally towards self-amplification. The occurrence of the aerodynamic resonance is closely related to the development of shock-induced separation, accompanied by quasi-steady inverse shock motion