Beyond the Frequency Limits of Time-Linearized Methods

摘要

Time linearized aerodynamic methods which usually operate in the frequency domainare known to suffer from frequency limitations especially in the transonic speed regime. Aerodynamic loads up to high frequencies are shown to be accurately obtained by applying methods which are based on exponentially diverging motions. A polynomial fit is made through the corresponding aerodynamic loads after which the fit is supposed to be valid also for general types of motion (analytical continuation). The convergence of iterative solvers in the aerodynamic methods is much improved, and a more than 50 percent reduction of computational cost may be achieved. It is further shown how existing time linearized methods which operate in the frequency domain can be modified to operate for diverging motions. Results of unsteady loads applications in two dimensional and three dimensional (3D) subsonic, transonic, and supersonic flow are shown. Results of an application to a 3D standard aeroelastic configuration in subsonic, transonic, and supersonic flow are presented. A description of the method of data fitting which was used in the examples is also given.