The General Flux/Source node, found under the
More submenu, adds the most general boundary condition for the Pressure Acoustics, Time Explicit model, as it is formulated (in the conservative form) for the discontinuous Galerkin method (dG). The condition defines the normal flux
gp and
gu at an exterior boundary, given by
where u = (
u,
v,
w) and
n = (
nx,
ny,
nz) in 3D and 2D, or
n = (
nr,
nφ,
nz) in 2D axisymmetric. Note that this condition is expressed in terms of the dependent variables and not the total fields. Care should be taken when using this advanced condition as the method is sensitive to proper formulation of boundary conditions. Only one characteristic can enter the domain at any boundary at the time, meaning that it is easy to overspecify the problem. Use the mesh normals (
nxmesh,
nymesh, and
nzmesh; or
nrmesh,
nphimesh, and
nzmesh) in the expression you define.
