IMPD (Impedance) vs. ABSR (Absorbing) Boundary Conditions

Our absorbing ABSR boundaries are advanced conditions designed to absorb energy at the boundaries for elastic and acoustic materials, linear and non-linear waves, and for multiple materials on the same boundary condition. It also works for broadband signals and varies angles of incidence.

IMPD impedance boundary conditions applies the mass and stiffness values of an infinite load of a given material on the boundaries stated. It will work like an absorber for plane waves across a reasonable frequency range (300% fractional bandwidth), and will be lower performance than ABSR under some conditions, but more stable in general.

Both can be used for fluids and solids, some of the wave types in elastic media will not be properly absorbed with the IMPD condition due to its limitation of primarily working with normal incidence waves.