Add an Enclosed Cavity node to indicate that certain boundaries represent a closed cavity within a solid. The Enclosed Cavity node primarily defines variables for the cavity volume in the undeformed and deformed configurations.

The cavity can be filled with a compressible or an incompressible fluid by adding a Fluid subnode, see Fluid (Enclosed Cavity). In this case, the pressure inside the cavity is governed by an equation of state, and the pressure changes when the enclosed volume changes due to external loads. It is also possible to apply a constant pressure, or an initial overpressure using the Prescribed Pressure node, see Prescribed Pressure (Enclosed Cavity).

The Enclosed Cavity node can be used without any subnodes. In this case, variables for the enclosed volume in the undeformed and the deformed configurations are created, and they can be evaluated typically during postprocessing.

The Enclosed Cavity node is only available with some COMSOL products (see https://www.comsol.com/products/specifications/).

This section is only visible if the Volume type is Open surface and Reference point is From selection. In that case, select one point, representing the reference point Xref.

Select the Volume type — Closed surface (default) or Open surface. Choose Open surface when the selected boundaries do not form a closed volume due to, for instance, mirror and sector symmetries, or a plane end cap.

For Open surface, select the Reference point — From selection (default) or User defined. The reference point, Xref, must be carefully selected according to the rules defined above.

Enter the Volume scale factor fV.

Physics tab with Solid Mechanics selected: