Numerical modelling and analysis of non-classical aileron buzz

A computational study is presented for non-classical aileron buzz considering the nonlinear effects of unsteady aerodynamics. It aims at using the classical approach of describing function technique with multiple input variables for the investigation of non-classical aileron buzz phenomenon. Limit cycle oscillatory behavior of an asymmetrical airfoil section has been studied initially using an expensive high-fidelity aeroelastic model which uses coupled CFD/CSD time marching approach. The aeroelastic model is based on a two dimensional wing section with rigid aileron integrated without gap. Flow model of Euler equations is coupled with dynamic equation of rigid rotation of aileron and is implemented in the solver AeroFoam. Results of numerical direct simulation are analyzed to obtain quality results which capture the key aspects involved in the shock dominated instability aeroelastic phenomenon. Further, outburst points of limit cycle parameters for varying Mach numbers and angles of attack are investigated. Using this high-fidelity aeroelastic model, a multiple input aerodynamic describing function is developed that can effectively represent the lumped nonlinearities of unsteady aerodynamics. It is demonstrated that limit cycle points can be closely identified through aerodynamic describing function representation formulated including only the fundamental harmonics contribution.