A Numerical Method for Scattering from Multi-domain Structures Based on Near-Field Artificial Boundary

Acoustic multi-connected domains are common in floating platforms and underwater vehicles. In order to improve the calculation efficiency of the traditional boundary element method and avoid dealing with complex connected domain boundary conditions, a method combining finite element method with artificial boundary element method is proposed to calculate the acoustic scattering of multi-domain structures.

In this work, based on near-field artificial boundary, the multi-domain fluid is divided into simple exterior domain and complex multi-connected interior domain. The FEM of Software Nastran is easy to employ for structures and complex multi-domain fluids. The artificial boundary element method is used to generate the exterior added fluid mass, added fluid damping and pressure load associated with incident wave. The codes developed by the author and DMAP language are used to generate the matrixes and to couple the FEM with artificial BEM.

The correctness and convergence of the proposed numerical method are further investigated. The simulation results are in good agreement with theoretical data and literature results. When the scale of the artificial boundary element is less than one tenth of the wavelength of sound wave, the calculated solutions tend to be stable. In the case of cavity scattering, compared with the traditional boundary element method, the calculation time of proposed method is reduced by nearly half with the same calculation accuracy.

Furthermore, the numerical method presented in this paper can solve scattering problems involving fluid spheres, bubbles, and multi-body structures, as well as the reflection of free water surfaces.