Adaptive multi-level substructuring for computing acoustic radiation and scattering from complex structures

Abstract

An adaptive method for computing acoustic radiation and scattering from complex structures is presented. The method uses a multi-level substructuring decomposition of a structure’s finite element model, in which the structure is partitioned into several substructures, and each of these is partitioned into its own substructures, and so on. For each substructure, the finite element representation is transformed to a new one in terms of a quasistatic dependence of internal degrees of freedom on interface and excited ones, complemented with response in substructure fixed-interface modes of vibration. This allows for model reduction in the form of modal truncation for substructures on various levels. The order of the model is reduced to the number of degrees of freedom excited by either the acoustic fluid or applied excitations, plus the number of modes included. An adaptive procedure is used to determine which substructure modes should be included in the structure model. The acoustic fluid is represented with a boundary element model, and the procedure for coupling the structure and fluid models is described. The method is demonstrated on numerical examples in three dimensions. [Work supported by ONR.]