NEW MODE TRACKING METHODS IN AEROELASTIC ANALYSIS

Within the context of analysis of finite element models, a methodology is developed for the tracking of complex eigenvalues and eigenvectors through changes in aeroelastic eigenvalue problems. The goal is to el iminate difficulties caused by mode switching (i.e., frequency crossin g). Two new methods for mode tracking are presented and compared with an existing method. The first new method, the complex higher order eig enpair perturbation algorithm, is based on a perturbation expansion of the eigenproblem. It iteratively computes changes in the eigenpairs d ue to parameter perturbations with the important feature of maintainin g the correspondence between the baseline and perturbed eigenpairs. Th e second new method is the complex cross-orthogonality check method wh ich uses mass biorthogonality of the left and right eigenvectors to re -establish correspondence after a standard reanalysis. Applications of mode tracking technology are presented in V-g and p-k subsonic aeroel astic analyses. Each application procedure is outlined and examples ar e given. Recommendations are made based on method ease of use and robu stness in the example problems.