Using this element to create an element optimized for solving wave equation using the discontinuous Galerkin method. The section settings for the
DG Wave Element, General Form node (
) are similar to the ones for the
General Form Equation node, with the following exceptions:
Use the Type list to select the type of the equation:
Normal (the default) and
Interior boundary source. The latter option can only be used in boundary conditions. Also note that boundary conditions do not support the
Γ and
da coefficients. Those settings are disabled for the
Interior boundary source type; otherwise they are simply ignored when the equation is used on a boundary.
For this element, the conservative flux Γ, the source term
f, and the damping or mass coefficient
da are applicable.
The Variable names field supports a comma-separated list of dependent variable names. It is important that you enter multiple dependent variables in the same order for all element nodes. Multiple dependent variables are necessary to allow cross-coupling in the
da and
Γ coefficients. All dependent variables must use the nodal discontinuous Lagrange shape function. For multiple dependent variables, the value of
N in the
Coefficients section is the sum of all lengths of the dependent variables.
From the Method list, choose
Lax-Friedrichs (the default) or
General for the method to compute the flux. For
Lax-Friedrichs, enter numerical values in the
Lax-Friedrichs flux parameter field with the length
N, the sum of all lengths of the dependent variables. For
General, enter a flux expression in the
Numerical flux field.
To include filter coefficients, select Always use filter (1),
Only use filter on absorbing layers (2), or
From expression from the
Filter rule list. The filter coefficients —
α,
η, and
s — can be NaN (not-a-number, which is the default value) to disable that filter coefficient. Each filter coefficient expects a scalar value. It is also possible to not include filter coefficients by selecting
Never use filter (0) from the
Filter rule list.
