New approximations of external acoustic–structural interactions: Derivation and evaluation

New approximate models for external acoustics interacting with flexible structures are developed. The basic form of the present models is obtained by a combination of the Laplace-transformed retarded and advanced potentials with the weighting parameter as part of the model equation. It is shown that the maximum attainable time-derivative of convergent approximate models is two, hence any attempt to include higher orders will lead to non-convergent models. The present external acoustic model is implemented and interfaced with a finite element structural analyzer for the transient response analysis of submerged spherical and cylindrical shells subjected to a series of incident waves. Comparisons of the present results with the classical analytical solutions and the Doubly Asymptotic Approximations (DAAs) show that proposed model offers improved accuracy especially for early-time responses, exhibits computational robustness, and maintains the impulse response consistency that are desirable for inverse problems. The present model is applied for a shock response correlation of an experimental complex ring cylinder, which demonstrates the applicability of the proposed approximate model to practical engineering problems.