Efficient Aeroelastic Analysis Using Computational Unsteady Aerodynamics

Abstract

A methodology for efe cient evaluation of generalized aerodynamic forces (GAFs) in transonic e ows for use in e utter analysis is presented. GAF matrices are evaluated from a reduced-order model (ROM), which comprises the generalized aerodynamic forces recorded from a time-accurate computational e uid dynamics (CFD) analysis in response to a modal step excitation in each structural mode. With the step response database, that is, the ROM, the comprehensive CFD analysis is replaced by a simple convolution scheme to compute the GAFs. The forces due to excitation of one mode at a given Mach number for all reduced frequencies can be computed from a single step response. Comparison of the GAFs computed from the ROM to those computed by direct sinusoidal excitation of the boundary conditions in a CFD run demonstrate, that for small amplitudes of excitation, the ROM is capable of predicting the unsteady aerodynamic forces very accurately. The use of ROM offers a signie cant reduction in computational time and makes the calculation of CFD-based unsteady aerodynamic forces for e utter analysis feasible. The CFD-based GAFs are used to conduct a e utter analysis of the AGARD 445.6 wing at several Mach numbers, and the results are compared to wind tunnel test results.