MODEL REDUCTION AND FREQUENCY WINDOWING FOR ACOUSTIC FEM ANALYSIS

Model degrees-of-freedom reduction and frequency windowing via interpolation are combined for application to acoustic finite element analysis problems. Projection operators are employed for the model reduction or condensation process. Interpolation is then introduced over a user defined frequency window, which can have real and imaginary boundaries and be quite large. Hermitian interpolation functions (which require derivative information) as well as standard Lagrangian functions, which can be linear, quadratic or cubic, have been used to construct the windows. For one-dimensional windows, the location of interior evaluation points can be varied to increase accuracy. Results are excellent for example problems, even for large d.o.f. reduction and large frequency windows containing numerous resonances (eigenvalues). The reduced models within the windows appear to indicate accurately the location of the resonances.