Use the Perforations node for applications in MEMS devices, where the phenomenon of squeeze-film damping is important. A free-hanging thin plate or the substrate often has an array of etch holes that allow the gas in between to escape. The perforations feature acts as a sink for gas that is proportional to both the ambient pressure and to the pressure difference with respect to the ambient on the other side of the perforated surface. The constant of proportionality is known as the admittance, Y, and it can either be defined directly or determined from the model due to Bao (Ref. 16). The ambient pressure is assumed to be the reference pressure pref specified in the Reference Pressure section.

Select a Perforation admittance — User defined (the default) or Bao model.

For User defined, enter a value or expression for Y (SI unit: m2⋅s/kg).

For Bao model, choose a Perforation shape — Square (the default) or Circular. Then enter the following inputs as applicable: