Calculation of Wing Flutter by a Coupled Fluid-Structure Method

An integrated computational  uid dynamics (CFD) and computational structural dynamics (CSD) method is developed for the simulation and prediction of  utter. The CFD solver is based on an unsteady, parallel, multiblock, multigrid Ž nite volume algorithm for the Euler/Navier–Stokes equations. The CSD solver is based on the time integration of modal dynamic equations extracted from full Ž nite element analysis. A general multiblock deformation grid method is used to generate dynamically moving grids for the unsteady  ow solver. The solutions of the  owŽ eld 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  utter 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–CSDmethod and the indicial method are presented and compared with experimental data for the AGARD 445.6 wing.