Interior Impedance/Pair Impedance

The and nodes add an impedance boundary condition on interior boundaries or boundaries between the parts of pairs. Add the node from the submenu. This condition is a generalization of the sound-hard and sound-soft boundary conditions. The condition corresponds to a transfer impedance condition, relating the pressure drop across the boundary

to the velocity at the boundary. In the frequency domain, it imposes the following equations:

For a Time Dependent study (time domain), the boundary condition uses the following equations:

On pair (interior) impedance conditions the up/down, that refers to the up and down side of an interior boundary, is replaced by a 1 and 2 index in the equation display. These refer to the two faces in the pair.

Zi is the transfer impedance, which from a physical point is the ratio between pressure drop and normal particle velocity.

	In the two opposite limits Zi → ∞ and Zi → 0, this boundary condition is identical to the Sound Hard boundary condition and the Sound Soft boundary condition, respectively. Additional information is found in Identity and Contact Pairs in the COMSOL Multiphysics Reference Manual.

Enter the value of the Zi (SI unit: Pa·s/m). The default is 0 Pa·s/m.