Adaptation of POD-based Aeroelastic ROMs for Varying Mach Number and Angle of Attack: Application to a Complete F-16 Configuration

Abstract

T he proper orthogonal decomposition (POD) method has been shown to produce accurate reduced-order models (ROMs) for the aeroelastic analysis of complete aircraft configurations at fixed flight conditions. However, changes in the Mach number or angle of attack often necessitate the reconstruction of the ROM in order to maintain accuracy, which destroys the sought-after computational efficiency. Straightforward approaches for ROM adaptation — such as the global POD method and the direct interpolation of the POD basis vectors — that have been attempted in the past have been shown to lead to inaccurate POD bases in the transonic flight regime. Alternatively, a new ROM adaptation scheme is proposed in this paper and evaluated for varying Mach number and angle of attack. This scheme interpolates the subspace angles between two POD subspaces, then generates a new POD basis through an orthogonal transformation based on the interpolated subspace angles. The resulting computational methodology is applied to a complete F-16 configuration in various airstreams. The predicted aeroelastic frequencies and damping ratio coefficients are compared with counterparts obtained from full-order nonlinear aeroelastic simulations and flight test data. Good correlations are observed, including in the transonic regime. The obtained computational results reveal a significant potential of the adapted ROM technology for accurate, nearl-real-time, aeroelastic predictions.