Aeroelastic Model Reduction for Affordable Computational Fluid Dynamics-Based Flutter Analysis

Abstract

A new approach is presented to generate computational fluid dynamics (CFD)-based reduced-order aerodynamic and aeroelastic models for rapid flutter analysis at an affordable cost. The technique is based on the single-composite-input/eigensystem realization algorithm (SCI/ERA) that has been newly developed at Boeing. Given a large-scaled, discrete-time CFD model whose moving surface boundary is described by multiple structural mode shapes, the SCI/ERA takes time samples of the unsteady response due to a simultaneous excitation of the inputs and identifies the aerodynamic system in terms of low-order matrices. Because the CFD response is sampled almost exclusively for the single representative input this technique can significantly reduce the model construction time. The reduced-order aerodynamic model is coupled with a discrete-time structural model to generate a reduced-order aeroelastic model. For a demonstration of the method, a representative Boeing wind-tunnel airplane modeled by a finite element method and the CFL3D CFD code is studied. It is shown that for the case of 10 structural modes the proposed scheme can reduce the model construction time by a factor of 4-6, yet its unsteady aerodynamic and flutter results are as accurate as those created by other reduction methods.