A novel generalized Bloch mode synthesis combined with the wave-based finite element method for modeling acousto-elastic periodic structures with strong fluid–structure interaction

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© 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/This paper addresses the modeling of acousto-elastic periodic structures with strong fluid–structure interaction, i.e., lattices in which both solid materials and heavy fluids coexist, and their mutual interactions cannot be neglected. Modeling is conducted with a single unit cell of the lattice using a novel Generalized Bloch Mode Synthesis combined with the Wave-based Finite Element Method (WFEM). Reduced-order unit cell models are derived through a multi-step model order reduction (MOR) procedure, duly accounting for the coupled dynamic behavior at fluid–structure interfaces and enabling exact enforcement of the Bloch–Floquet theorem. These reduced-order models are used within the WFEM framework to quickly obtain accurate responses, without encountering numerical issues. Various unit cell geometries are examined, ranging from simpler to more complex, with fluid confined to internal cavities or distributed throughout the lattice. Both water and mercury are considered as fluids in simulations. Results demonstrate that highly reduced unit cell models are obtained with the proposed MOR strategy; accurate solutions are achieved when the reduced-order models are combined with the WFEM; the dynamic behavior of a manufactured periodic structure with confined fluid is accurately assessed; and the modeling framework performs very well irrespective of the unit cell geometry, symmetry and fluid type.

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