The Interior Impedance node, found under the
Interior Conditions submenu, adds an interior boundary condition to prescribe a transfer impedance between two domains. The condition defined a relation between the local total acoustic pressure jump
pt,up_
−_
pt,down (difference between upside and downside of the boundary) and the normal acoustic velocity
n·ut, that is, the specific acoustic transfer impedance
Zn. The condition also prescribes continuity in the normal velocity across the boundary. The condition reads
A pair version of this feature the Pair Impedance exists for use in geometry assemblies on pair. In this case, the pressure jump is computed from the source (
src) to the destination (
dst).
Enter a value or expression for the Specific transfer impedance Zn (SI unit: Pa·s/m). The default expression is
pate.c*pate.rho which is the characteristic specific impedance
ρc of a propagating plane wave.
This section is only present for the Pair Impedance condition. The time-explicit DG-FEM method uses an efficient quadrature free computation of the boundary flux. This can in certain cases result in unstable behavior when pair conditions are used with non-conforming meshes. To remedy this a more accurate projection based quadrature method is used (per default) on all pair conditions, such as the
Pair Impedance condition.
