A variable order infinite element for multi-domain boundary element modelling of acoustic radiation and scattering

A direct collocation multi-domain boundary element method for acoustic radiation and scattering problems in unbounded domains is introduced. For effective modelling of the acoustic field variables along the infinite interfaces of adjacent subdomains a new infinite boundary element is formulated. The element is based on a finite to infinite geometry mapping and a special shape function of variable order combining an appropriate amplitude decay and wavelike variation. The direct collocation scheme is of particular interest when modelling different acoustic media in adjacent subdomains. Other benefits of this multi-domain boundary element method include banded system matrices for better computational efficiency and the fact that no singularities are present due to the non-uniqueness problem, common for conventional boundary integral methods. Both two-dimensional and axisymmetric modelling of acoustic radiation and scattering problems are presented.