Vibroacoustic frequency sweep analysis using automated multi-level substructuring

An algorithm for frequency sweep analysis of complex structures interacting with a light acoustic fluid is presented. The structure finite element model is transformed to a very efficient representation, in terms of eigenvectors for thousands of substructures on dozens of levels, using Automated Multi-Level Substructuring. Response of the fluid is in terms of the fluid's modes of vibration, calculated from a fluid finite element representation in terms of nodal pressures. The sweep algorithm uses a two-part representation of the response. The first part includes the response of low-frequency global structure modes, approximated in terms of substructure modes, and nearly resonant fluid modes. The second part includes the response of all substructure modes and all non-resonant fluid modes, up to appropriate cutoff frequencies.