System identification and proper orthogonal decomposition method applied to unsteady aerodynamics

The representation of unsteady aerodynamic flowfields in terms of global aerodynamic modes has proven to be a useful method for reducing the size of the aerodynamic model over those representations that use local variables at discrete grid points in the flow field. Eigenmodes and proper orthogonal decomposition modes have been used for this purpose with good effect. This suggests that system identification models may also be used to represent the aerodynamic flowfield. Implicit in the use of a systems identification technique is the notion that a relative small state-space model can be useful in describing a dynamical system. The proper orthogonal decomposition model is first used to show that indeed a reduced-order model can be obtained from a much larger numerical aerodynamical model (the vortex lattice method is used for illustrative purposes), and the results from the proper orthogonal decomposition model and the system identification methods are then compared. For the example considered the two meth ods are shown to give comparable results in terms of accuracy and reduced model size. The advantages and limitations of each approach are briefly discussed. Both appear promising and complementary in their characteristics.

Duke Scholars

Author Earl H. Dowell Thomas Lord Department of Mechanical Engineering and Materia ...