Efficient Calculation of Aerodynamic States for Aeroelastic Analyses in the Frequency Domain

Abstract

The current paper is concerned with studying different forms of generating the aerodynamic operator, with the use of computational fluid dynamics (CFD) techniques, for performing transonic aeroelastic stability analyses in the frequency domain. The CFD calculations are based on the Euler equations and the code uses a finite volume formulation for general unstructured grids. A centered spatial discretization with added artificial dissipation is used, and an explicit Runge-Kutta time marching method is employed. The dynamic system being considered in the present work is a NACA 0012 airfoil-based typical section in the transonic regime. Unsteady calculations are performed for mode by mode and simultaneous excitation approaches. The simultaneous inputs used are based on orthogonal Walsh functions. The use of system identification techniques is employed to allow the splitting of the aerodynamic coefficient time histories into the contribution of each individual mode to the corresponding aerodynamic transfer functions. The present approach is validated against aerodynamic transfer functions obtained by indicial excitation of each individual mode. The results are in good agreement with the literature data and, hence, the procedure implemented accomplishes the desired goal of obtaining the aerodynamic operators for aeroelastic analyses with a single unsteady CFD calculation.