Techniques for Reduced Order Modeling of Aeoelastic Structures with Deforming Grids

摘要

Reduced order modeling (ROM) seeks to make the modeling of aeroelastic behavior practical by reducing computation time for design codes. Deforming grids are often used in aeroelastic problems to account for the deformation of the structure. Proper Orthogonal Decomposition (POD/ROM) is a ROM technique that operates in an index-space for computations, not accounting for changes in grid dynamics, and must be modified to reflect grid deformation properly. To investigate and account for the effects of grid deformation on POD/ ROM, a new algorithm is developed that incorporates modifications to the usual formulation. Evaluation of the new algorithm is accomplished through application to three fluid-structure models, each adding an increased level of grid dynamics. Deforming grid POD/ROMs are found to require more modes for an accurate solution than POD/ROM for rigidly moving grids. In addition, for deforming grids, POD/ROMs are less accurate when the grid deformation is significantly altered from the deformations seen in the development of the POD/ ROM. A technique, called Multi-POD, is developed that evaluates the relative grid motion between how the POD/ROM is created and how it is executed. The Multi-POD technique determines the current relative grid deformation and selects the best POD/ROM from those available.