Quasisteady aerodynamics for flutter analysis using steady computational fluid dynamics calculations

Abstract

A quasisteady method is presented where the results of steady computational fluid dynamics (CFD) calculations are used to obtain generalized aerodynamic forces for flutter analysis. For high-speed flows, the method provides a bridge between the computational efficiency, but relative, inaccuracies of piston theory and the greater accuracy, but high, computational cost of CFD flutter calculations. The method uses the structure's vibratory modes to modify the boundary conditions in the steady CFD calculations. Two steady CFD solutions are required per vibratory mode: one for the static part and one for the harmonic part of the pressure distribution. The pressure distributions of these solutions can be used to compute generalized aerodynamic forces necessary for flutter analysis. Sample two- and three-dimensional aerodynamic force calculations are provided demonstrating the method, and a flutter analysis of a National Aerospace Plane type wing is also discussed.