Explanation of AEROSTABIL limit-cycle oscillations via high-fidelity aeroelastic simulations

Kurzfassung

This thesis deals with the physical understanding of the limit-cycle oscillations (LCO) of the AEROSTABIL wing model by means of computational simulations. The LCOs have been measured by Dietz et al. (2003) in the Transonic Windtunnel Göttingen in 2002/2003. Aeroelastic high-fidelity CFD-CSM methods have been developed and applied to simulate these transonic, clean wing LCOs. The aeroelastic methods include a versatile CFD-CSM coupling method, CFD mesh deformation with radial basis functions, steady and unsteady fluid-structure interaction as well as unsteady forced motion methods for frequency domain analysis. To find a convincing AEROSTABIL LCO statement the available experimental pressure and acceleration data have been used to validate the computations. Static aeroelastic investigations are the starting point: Here the AEROSTABIL model revealed strong profile cambering. Only a detailed structural model allowed the accurate prediction of these deformations and the measured static pressures. An additional experiment including the AEROSTABIL wing verified the profile deformations. The accuracy of the resulting static pressures is very important to allow the simulation of the unsteady LCO phenomena. Furthermore, the profile cambering must be incorporated into the unsteady investigations as well. Flow features at LCO conditions are very challenging for the applied aerodynamic method. The double-shock system plus flow separation could only be predicted with sufficient accuracy by certain turbulence models. The aerodynamically driven LCO could be explained by strong shock movement in the outer wing area. It is revealed that this effect leads to a nonlinearly reducing wing excitation with increasing motion amplitude. Overall, an important scientific contribution of the studies is to show the potential accuracy of state of the art aeroelastic methods.