Numerical calculation of flutter derivatives via indicial functions

The central focus of the present study is the numerical calculation of flutter derivatives. These aeroelastic coefficients play an important role in determining stability, or rather, instability of long, flexible structures under ambient wind loading. In recent years, the Finite Element Method (FEM) has gained considerable acceptance in the solution of problems governed by the viscous, incompressible flow equations. FIDAP is one such general fluid dynamics analysis package that makes use of Finite Element methodology. The most direct way of obtaining flutter derivatives would be to simulate the full oscillatory object motion in a flow and use the unsteady lift and moment forces thus determined. This would essentially entail an internal boundary motion in the flow, which requires considerable computational effort in the case of most Eulerian non-adaptive grid-based numerical methods. However, the alternative indicial function approach investigated in this study limits itself to step changes in motional variables. Inherent to using this approach, then, is the assumption of reduced computational complexity. (C) 1996 Academic Press Limited