The General Flux/Source node, found under the
More submenu, adds the most general boundary condition for the convected wave equation, as it is formulated (in the conservative form) for the discontinuous Galerkin method (dG). The condition defines the normal flux
g at an exterior boundary, given by
where u = (
u,
v,
w),
u0 = (
u0,
v0,
w0), and
n = (n
x, n
y, n
z) (
n = (n
r, n
φ, n
z) in 2D axisymmetric) is the surface normal. 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 over-specify the problem. Use the mesh normals (
nxmesh,
nymesh, and
nzmeshor; or
nrmesh,
nphimesh, and
nzmesh) in the expression you define.
