Experimental analysis of wave propagation at buffet flows

Modern transport-type wings with supercritical airfoils are characterized by a local supersonic flow field on the upper surface terminated by a shock. A highly complex and time-dependent flow pattern can exist in the direct vicinity of the wing surface with a shock-induced separation of the turbulent boundary layer. At certain flow conditions, this may lead to self-sustained oscillations of the shock wave which may lead to critical unsteady loads of the wing structure due to the generated pressure fluctuations. The nature and the mechanisms behind the so-called buffet phenomenon is not yet fully understood. Detailed experimental data of the transonic buffet flow field over a supercritical DRA 2303 airfoil is obtained in this thesis targeting the deeper understanding of the origin and nature of the unsteady shock-boundary-layer interaction and the influence of the structural motion on the shock oscillation. Furthermore, the aeroelastic response of the shock oscillations is investigated using an elastic support of the airfoil model that allows a coupled elastic heave and pitch motion of the rigid model. Forced sinusoidal heave/pitch motion at frequencies in the range of the natural buffet frequency of the airfoil is applied to the model. Results at varying oscillation frequencies are compared to the corresponding purely aerodynamic flow field providing direct and implicit insight into the buffet and buffeting mechanisms.