Acoustic impedance is difficult to grasp intuitively since it is dependent on both material and geometry and is complicated by the fact that the velocity and pressure are not necessarily in phase. Yet it is critical that engineers get it right because it dictates efficient transfer of sound energy from point to point.
For many years, ANSYS has had 2D and 3D acoustic elements, including those used to model an "infinite" boundary. These elements can be used in modal, harmonic, and transient analyses, and fluid-structural interaction can also be accounted for in these simulations. The application of complex impedance on a boundary can be performed in ANSYS with the use of SURF153/154 elements.
The use of SURF153/154 allows users to model complex specific acoustic impedance at any boundary. The user, however, should run smaller models with known solutions first to become acquainted with this slightly unconventional modeling approach. The unique feature of these elements is that terms to the mass [M], damping [C], or stiffness [K] matrices can be added directly.