Evaluation of Generalised Forces Using CFD-Based Methods for Efficient Linear/Nonlinear Simulations
The development of efficient and accurate Reduced-Order Models (ROMs) for transonic aeroelastic systems with freeplay poses a significant challenge for aeroelasticians, requiring linearization of both nonlinear structural and aerodynamic systems. In this paper, well established aerodynamic and structural model order reduction methods are rigorously assessed for their usability, efficiency and accuracy when applied an all-movable tail model with freeplay in the transonic flow regime. Two methods for augmenting the structural modal basis are considered, namely fictitious masses (FM) and residual vectors (RV), while the transonic aerodynamic forces are modeled using CFD-based aerodynamic impulse response functions. The results demonstrate that under full nonlinear fluid loading conditions both the FM and RV approaches perform excellently (against the benchmark full CFD-CSD solution). When considering linearized aerodynamic loading, the FM model outperforms RV. The limitations of the linearized aerodynamic ROM are also assessed, demonstrating a significant reduction in accuracy for freeplay values greater than 0.1◦.
