The Acoustic Impedance (Isentropic) adds a simple acoustic impedance assuming isentropic (adiabatic) behavior for the fields. This condition should be used with care as it is not necessary that the solution is isentropic near a boundary. The impedance based on Myers’ work is given by the Impedance and Interior Impedance conditions. The isentropic impedance conditions reads:

In transient models, use this boundary condition in combination with the Absorbing Layers for the Linearized Euler, Transient Interface to create efficient nonreflection conditions.

Enter an expression or value for the Impedance Zi (SI unit: Pa·s/m). The default value is set to let.rho0*let.c0, which is the specific characteristic impedance of a plane propagating wave.

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