Impedance
Use the Impedance node to specify a normal specific impedance Zn on a boundary. Add this node from the Mechanical submenu. This feature is useful outside the viscous boundary layer, as this condition mimics the behavior of a corresponding Pressure Acoustics Model with a normal impedance condition. The boundary condition reads
The condition relates the normal stress at the boundary to the normal velocity, through the value if the specific impedance.
Mechanical
Enter a value or expression for the Specific impedance Zn (SI unit: Pas/m).
Select a condition for the Tangential velocitySlip (the default) or No slip. The No Slip option will apply an additional constraint for the velocity in the tangential direction on the boundary.