Problem description
The model is a semicircular shell and fluid mesh of radius 2.286 m. A point load on the symmetry axis of magnitude 1.0 N is applied to the shell. The shells are 0.0254 m in thickness and have a Young's modulus of 206.8 GPa, a Poisson's ratio of 0.3, and a mass density of 7800.0 kg/m3. The acoustic fluid has a density, , of 1000 kg/m3 and a bulk modulus, , of 2.25 GPa. The response of the coupled system is calculated for frequencies ranging from 100 to 1000 Hz in 5 Hz increments. There are two different finite element meshes used: one with explicitly defined acoustic-structural interaction elements and one that uses a tie constraint. The former model consists of 220 SAX1 elements surrounding a mesh of 15848 ACAX4 elements. Coupling is effected using 220 ASI2A elements. The latter model uses 80 SAX2 elements surrounding a mesh of 965 ACAX8 elements. For this mesh, coupling is effected using a tie constraint to generate the acoustic-structural interaction elements internally.
A dummy part is included in the models to ensure that the analytical solution appears in the output database. This part consists of a single point mass, uncoupled from the model described above, with a displacement boundary condition on degree of freedom 1. This imposed displacement uses an amplitude table consisting of the Stepanishen/Cox analytical solution for the drive point admittance.