The Elastic Waves, Time Explicit Interface includes so-called
absorbing layers, also often referred to as
sponge layers. The layers work by combining three techniques: a scaling system, filtering, and a low-reflecting condition.
The layers are set up by adding the Absorbing Layer under the
Definitions node. This adds a special scaled system. The scaling effectively slows down the propagating waves and ensures that they “align up” (normal) toward the outer boundary. This means that the waves will hit the outer boundary in a closer to normal direction. Filtering attenuates and filters out high frequency components of the wave. The filter parameters are controlled under the
Filter Parameters for Absorbing Layers section at the main physics level. Finally, at the outer boundary of the layer add a
Low-Reflecting Boundary condition, which will work well to remove all remaining waves, as normal incidence has been ensured.
For the Absorbing Layers select the
Type (
Cartesian,
Cylindrical,
Spherical, or
User defined) under the
Geometry section. Enter values for the
Physical Width and
Pole Distance under the
Scaling section.