Improved mode tracking for the p-L flutter solution method based on aeroelastic derivatives

Abstract

In this work an improved mode tracking algorithm is developed for the p-L flutter solution method. Compared to the original criterion used for sorting the aeroelastic modes, the approach presented herein uses aeroelastic derivatives in order to predict the flutter solution at the next parameter value. The present method allows for a more robust and efficient sorting of the aeroelastic modes for configurations where the number of real and complex poles resulting from the representation of the aerodynamic term is high, ensuring a proper tracking of the modes corresponding to the structural degrees of freedom. The flutter p-L method together with the proposed mode tracking algorithm is applied to a 2 degrees-of-freedom airfoil configuration with high-fidelity unsteady aerodynamics and to the common research aeroelastic model representing a transport aircraft configuration. For the latter, a modified doublet-lattice method valid throughout the complex plane is used for the reference solution, allowing for the first time to validate the p-L flutter solution method for general configurations. The results show that the p-L method is able to truly represent the aeroelastic damping when compared to the classical p-k and g methods.