An infinite element for the solution of Galbrun equation

In this article we present a method for the three-dimensional numerical simulation of the propagation of acoustic radiation inside and in the near field of long, slender, and hollow objects. While the fluid inside and close to the radiating body is meshed by Taylor-Hood tetrahedral finite elements, complex conjugated Astley-Leis infinite elements are added on the outer finite element boundary to present the effects in the far field. Flow is considered in the modal analysis, with the goal to determine the influence a moving fluid has on the eigenfrequencies of the model. Galbrun equation in a mixed, meaning pressure and displacement based, formulation is used for the numerical realization and its weak form is presented for the finite element domain as well as for the infinite element domain.