Accuracy and Stability of Finite Element Schemes for the Duct Transmission Problem

A one-dimensional numerical model is used to investigate the characteristics of finite element computational schemes for linearized acoustical transmission in ducts with flow. Primitive variables and coupled first-order equations are used. The relative performances of Lagrangian and Hermitian elements with Galerkin and residual least squares formulations are assessed. Results of the numerical study are shown to correlate with the characteristics of analytic solutions for the equivalent regular grid difference equations. Galerkin solutions are shown to introduce spurious nonphysical modes which must be eliminated by careful attention to the local resolution requirements of the finite-element mesh. Residual least squares formulations do not introduce spurious numerical modes but result in significant numerical damping