Reduced Order Modeling For Transonic Flutter Analysis

Transonic aerodynamics present significant challenges for aeroelastic analysis due to nonlinear phenomena such as strong shock waves and flow separation. For aeroelastic analyses, the unsteady aerodynamic model must accurately predict the aerodynamic loads, or generalized forces, resulting from the structure’s static shape and its dynamic motion. Linear aerodynamic models commonly used in flutter analysis (e.g., the Doublet Lattice Method) often fail to accurately predict flutter in transonic conditions, necessitating higher-fidelity aerodynamic modeling. Alternatives are Computational Fluid Dynamics (CFD) models of different fidelity, which can be used to compute the transonic aerodynamics and aeroelastic responses. However, the computational cost of CFD simulations limits their application to complex configurations. Therefore, CFD-based flutter prediction is often carried out using reduced-order models (ROMs) of the unsteady aerodynamics, which are coupled with the structural dynamic model. The current study suggests a time-domain Multi-Output Auto-Regressive formulation for the unsteady aerodynamic model. The model is applied to the transonic Benchmark Supercritical Wing (BSCW) airfoil at various angles of attack to explore the range of validity of this modeling approach. The resulting ROM is used to investigate the flutter envelope of the spring-suspended BSCW airfoil across a range of transonic conditions, with results compared to those from fully coupled aeroelastic simulations.