Numerical Analysis of the Aeroelastic Properties of a Wind-Tunnel Model with a Forward Swept Laminar Wing

Abstract

The influence of a laminar boundary-layer on the aeroelastic stability is an important subject of research in the field of aeroelasticity, in particular at Reynolds numbers for real flight conditions. Of great importance are effects due to the compressibility of the flow, which cause a reduction of the flutter velocity as a result of compressibility shocks. Since the shock is significantly influenced by the condition of the boundary-layer, this can potentially result in substantial differences in terms of the aeroelastic stability. This thesis analysis the static and dynamic aeroelastic stability of a wind-tunnel model with a forward-swept laminar wing on the basis of numerical models as a prearrangement of a wind-tunnel experiment in the cryogenic European Transonic Windtunnel (ETW). The analyses is performed through the application of high-fidelity coupled simulations of aerodynamic and structural models. The aerodynamic simulations are realised through the application of a Reynolds-averaged Navier-Stokes method for a wing-fuselage combination as a half-model and a far-field mesh. The simulations are carried out for transitional and fully-turbulent boundary-layers within the flow envelope of the ETW. For this purpose, the gamma transition model, as well as the Menter-SST k-omega and Spalart-Allmaras turbulence models are applied. The results of a transitional and fully-turbulent boundary-layer are compared to each other in order to analyse the influence of a laminar boundary-layer. In terms of the structural simulations, generic finite-element models of different complexity are applied. In this context, it will be analysed how the modelling of so-called pockets, which provide the required space for the installation of measurement equipment inside the model, influence the deformation behaviour of the structure. Additionally, the stiffness of the pitching motion is varied at the clamping of the model in order to analyse the flutter behaviour of the model under critical conditions. The results show that the aerodynamic loads are generally higher for a laminar compared to a fully-turbulent boundary-layer, which causes higher deflections of the model. The neglect of the cavities inside the structural model leads to lower static deformations. However, the resulting aerodynamic loads are underestimated only marginally. In general, there is no risk for flutter due to the high stiffness of the model. A flutter case is only present through the substantial decrease of the torsional spring stiffness at the clamping. The flutter velocity is thereby generally only slightly lower for a transitional compared to fully-turbulent boundary-layer. Furthermore, the model is stable in terms of torsional divergence for all analysed cases.