Numerical Validation of a High-aspect Ratio Wing Flexible Aircraft Modelled in an Enhanced Low-fidelity Framework

Kurzfassung

The aviation industry has been continuously seeking forms to enhance the aircraft aerodynamic efficiency, thereby reducing its environmental impact. One focus has been reducing the aircraft weight while maximizing its lift-to-drag ratio by applying slender elongated wings, the so-called High-Aspect-Ratio (HAR) wings. These lightweight HAR wings introduce substantial structural flexibility to the vehicle, which in turn may cause a problematic coupling between aeroelasticity and flight dynamics. Predicting these phenomena is even more challenging when flying in the transonic regime. The integration of Computational Fluid Dynamics (CFD) and Computational Structural Dynamics (CSD) formulations allows the characterization of phenomena occurring in this regime. However, despite recent advances in computational performance, modern CFD/CSD solvers still require massive simulation time and are therefore unsuitable for many tasks, such as flight and aeroelastic control law design and verification. To address this problem, low fidelity frameworks for the simulation of the flexible aircraft dynamics have been proposed, which offer high computational performance while resembling higher complexity models well enough so that control design, testing and flying quality analyzes are possible. However, the consideration of transonic effects is still a problem in these low-fidelity models. In this work, a CFD-based correction form for transonic effects in a low-fidelity model of the flexible aircraft dynamics using strip theory is studied. The derived model is numerically validated for the DLR-F25 virtual reference aircraft through a comparative analysis of its longitudinal behavior against CFD data in the time and frequency domain. The results show a good qualitative and quantitative agreement of the rigid body and flexible flight dynamics in both domains. They therefore reinforce the ability of the proposed framework to capture complex transonic aeroelastic effects with high computational efficiency.