FEM/FEM versus FEM/BEM vibro-acoustic coupling techniques applied to the Brazilian Vehicle Satellite Launcher (VLS) fairing problem: Advantages and drawbacks

Resumo

Fluid-structure interactions are always present in real life dynamic systems, during operations. However, analysts, due to the complexity of building a vibro-acoustic model and also because sometimes the coupling effect has no significance, often apply "one way" analysis, or uncoupled analysis. This analysis procedure is done in two steps, on which the structural part and the fluid part are modeled separately. Nevertheless, sometimes it is important to consider the mutual influence of the vibro-acoustic system, where the acoustic and structural matrices are coupled and the influence of the structural displacement on the fluid domain, as well as the acoustic pressure of the fluid domain on the structural body, are accounted in one coupled matrix. Low frequency coupling techniques, or deterministic coupling techniques, were used to calculate the Brazilian Satellite Launcher Vehicle (VLS) fairing behavior. The well-known structural FEM/fluid FEM technique and structural FEM/fluid BEM technique were applied to model the fairing body and its acoustic cavity. Calculations were done, which yielded the low frequency acoustic cavity as well as the skin responses. This paper describes the applied procedures to build up the vibro-acoustic models of the VLS. The obtained results are described and a comparison between FEM/FEM versus FEM/BEM techniques is presented. In such a comparison, parameters as computational efficiency, allocated memory, processing time, obtained results and modeling are considered.