Use the Perforations node for applications in MEMS devices, where the phenomenon of squeezed 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 can either be defined directly or determined from the model due to Bao (M. Bao and H. Yang “Squeeze film air damping in MEMS”, Sensors and Actuators A: Physical, vol. 136, no. 1, pp. 3–27, 2014). The ambient pressure (defined at the level of the parent physics interface or Thin-Film Damping feature) is assumed to be the reference pressure specified at the physics interface level.

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 as applicable: