Flight Dynamics Mode Identification and Model Reduction using Computational Fluid Dynamics

Copyright © 2016 by G. Pagliuca and S. Timme. Published by the American Institute of Aeronautics and Astronautics, Inc. A reduced order model for free-flight test cases is presented considering the coupling of flight dynamics and aerodynamics arising from computational fluid dynamics. The formulation relies on an expansion of the full order non-linear residual function in a truncated Taylor series and subsequent projection using modes of the coupled system. Free-flight effects are included in the reduced order model by means of flight dynamics modes identified with either of two approaches. The first technique is based on the Schur decomposition of the coupled Jacobian matrix tracing the eigenvalues emerging from the rigid-body degrees-of-freedom. The second method pre-computes dynamic derivatives which are then used to identify the flight dynamics modes. The reduced order model is expanded to simulate gust encounter. All methods are applied to a two-dimensional aerofoil in transonic flow showing results for initial disturbance and gust simulations. The reduced order model is capable of reproducing full order results accurately.