Applications of velocity potential function to acoustic duct propagation using finite elements

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Applications of velocity potential function to acoustic duct propagation using finite elements

Baumeister, K.J. / Majjigi, R.K.

A finite element velocity potential program has been developed for NASA Lewis at the Georgia Institute of Technology to study acoustic wave propagation in complex geometries. For irrotational flows, relatively los sound frequencies, and plane wave input, the finite element solutions show significant effects of inlet curvature and flow gradients on the attenuation of a given acoustic linear in a realistic variable area turbifan inlet. In addition, as shown in the paper, the velocity potential approach can not be used to estimate the effects of rotational flow on acoustic propagation since the potential acoustic disturbances propagate at the speed of the media in sheared flow. Approaches are discussed that are being considered for extending the finite element solution to include the far field as well as the internal portion of the duct. A new matrix partitioning approach is presented that can be incorporated in previously developed programs to allow the finite element calculation to be marched into the far field. The partitioning approach provides a large reduction in computer storage and running times. (DePo)