Flutter computations of complex configurations using cartesian grids

Abstract

We present in the paper a practical approach to compute the fluid-structure interaction of complex configurations. A Cartesian-based Euler solver with embedded multi-grid sequencing is used for the flow computation. The Cartesian approach significantly simplifies the process of grid generation for complex configuration. The unsteady flow computation is performed on a set of stationary Cartesian grids using the small perturbation techniques. The full boundary conditions for the Euler equations on the moving surface are replaced by approximate boundary conditions on the stationary grid. On the structural side, the modal superposition technique is applied to analyse the structural response under the action of the aerodynamic forces. The coupling between the fluid and structure domains is implemented using the Constant Volume Tetrahedron (CVT) transformation method, by which the aerodynamic forces are transferred to the structural domain and the structural deformation to the fluid domain. This enables a tight fluid-structure coupling. The present numerical scheme is applied in flutter analysis of an AGARD 445.6 wing and of a complete aircraft. In the former case, results are compared with published results in order to demonstrate the present numerical scheme. In the latter case, the complex shape of the NORTHROP F-5E TIGER II with wing-tip missiles is used to demonstrate the overall capability of the present scheme.