Convergence criteria on the acoustic velocity continuity in a panel-cavity system.

Modal-based acoustoelastic formulation is regarded as the cornerstone of vibro-acoustics and has been widely used for coupling analyses of structure-cavity systems. The controversy and the skepticism surrounding the acoustic velocity continuity with the surrounding vibrating structures have been persistent, calling for a systematic investigation and clarification. This fundamental issue of significant relevance is addressed in this paper. Through numerical analyses and comparisons with wave-based exact solution, an oscillating convergence pattern of the calculated acoustic velocity is revealed. Normalization of the results leads to a unified series truncation criterion allowing minimal prediction error, which is verified in three-dimensional cases. The paper establishes the fact that the modal based decomposition method definitely allows correct prediction of both the acoustic pressure and the velocity inside an acoustic cavity covered by a flexural structure upon using appropriate series truncation criteria.