Add a Prescribed Pressure under an Enclosed Cavity node to apply a known, constant pressure. This feature can be used to model a constant pressure inside the cavity, or when there is an initial overpressure in the cavity in addition to pressure changes resulting from wall deformations.

An example for the latter case is a vehicle tire, which in a first step is pressurized to a certain known overpressure. In a second step, the tire may be deformed due to external loads such as when the tire is pushed on the ground, and deforms further due to the vehicle’s weight. This type of analysis requires two study steps. In the first step, only the initial overpressure is applied in order to compute the deformed volume. In the second step, the initial overpressure must be maintained, while additional pressure changes occur due to the external deformation of the volume. These additional pressure changes can be modeled by adding a Fluid subnode, see Fluid (Enclosed Cavity), and entering appropriate values for the reference pressure and reference volume, respectively. The reference volume must be equal to the deformed volume from the first step.

The Prescribed Pressure node is contributing with itself and the Fluid node.

Enter the Pressure p.

Physics tab with Enclosed Cavity selected in the model tree: