Aeroelastic Applications of PERMAS.

Abstract

The determination of aeroelastic stability and dynamic response requires a coupling of structural and aerodynamic mathematical models rather than the solution of structural equations for given air loads or the solution of aerodynamic equations for given motion. Aeroelastic models are built from various sources, both experimental and theoretical. The calculations are based on ground vibration test results or finite element idealizations. A modal approach is generally used to calculate flutter stability via a non-standard eigenvalue problem which must be solved iteratively for given flow conditions. Mode shape data is necessary to determine generalized airloads. Depending on the aerodynamicist's choice of idealization and of the method to be applied, modal deflections and slopes determining the downwash must be available at points that are not considered in advance by the structural dynamicist. Also, the air loads must be integrated according to the virtual work principle. The problem of interpolation is addressed and different solutions are presented. This paper also presents some results of current sailplane flutter calculations using PERMAS finite element models. Extensions of PERMAS for future use as a tool in aeroelastic applications are proposed.