Doubly asymptotic multi-directional transmitting boundary for dynamic unbounded medium-structure-interaction analysis

The novel doubly asymptotic multi-directional transmitting boundary combines the advantages of the doubly asymptotic and multi-directional formulations. It is rigorous for the low-frequency limit (static case) and the high-frequency limit in the wave-propagation direction perpendicular to the artificial boundary and at all the preselected angles corresponding to various apparent velocities. It is implemented straightforwardly in the finite-element method. The doubly asymptotic multi-directional transmitting boundary is temporally local and spatially either global or local depending on the implementation of the static-stiffness matrix. It leads to much higher accuracy than other transmitting boundaries with the same finite-element mesh.