Calculation of wing flutter by a coupled fluid-structure method

An integrated computational fluid dynamics (CFD) and computational structural dynamics (CSD) method is developed for the simulation and prediction of flutter. The CFD solver is based on an unsteady parallel, multiblock, multigrid finite volume algorithm for the Euler/Navier-Stokes equations. The CSD solver is based on the time integration of modal dynamic equations extracted from full finite element analysis. A general multiblock deformation grid method is used to generate dynamically moving grids for the unsteady flow solver. The solutions of the flow-field and the structural dynamics are coupled strongly in time by a fully implicit method. The coupled CFD-CSD method simulates the aeroelastic system directly on the time domain to determine the stability of the aeroelastic system. The unsteady solver with the moving grid algorithm is also used to calculate the harmonic and/or indicial responses of an aeroelastic system, in an uncoupled manner, without solving the structural equations. Flutter boundary is then determined by solving the flutter equation on the frequency domain with the indicial responses as input. Computations are performed for a two-dimensional wing aeroelastic model and the three-dimensional AGARD 445.6 wing. Flutter boundary predictions by both the coupled CFD-CSD method and the indicial method are presented and compared with experimental data for the AGARD 445.6 wing.