You can create a fluid cavity pressure boundary condition to control the pressure in a cavity throughout the analysis. The fluid cavity pressure is associated with a fluid cavity interaction. It is used to determine flow for a fluid exchange interaction. You can change the fluid cavity pressure throughout the analysis by assigning a new value for the step and an amplitude to define the rate of change from the previous value. (For more information, see “Initial conditions in Abaqus/Standard and Abaqus/Explicit,” Section 34.2.1 of the Abaqus Analysis User's Guide.)
To specify a fluid cavity pressure:
Display the fluid cavity pressure boundary condition editor using one of the following methods:
To create a new fluid cavity pressure boundary condition, follow the procedure outlined in “Creating boundary conditions,” Section 16.8.2 (Category: Other; Types for Selected Step: Fluid cavity pressure).
To edit an existing fluid cavity pressure boundary condition using menus or managers, see “Editing step-dependent objects,” Section 3.4.13.
If a Method field appears toward the top of the editor, click the arrow to the right of the field, and select one of the following:
Select Specify pressure if you want to specify a value for the fluid cavity pressure.
Select Fixed at current pressure if you want to fix the fluid cavity pressure magnitude at its final value from the previous general step.
If a Fluid cavity interaction field appears, click the arrow to the right of the field, and select the interaction to which the pressure applies.
The Fluid cavity interaction option appears in the editor only if you are creating a new boundary condition or if you are editing the fluid pressure boundary condition in the step in which it was created. The interaction cannot be changed when editing the boundary condition in a propagated step.
If a Fluid cavity pressure field appears, enter a value for the current step.
If applicable, click the arrow to the right of the Amplitude field, and select the amplitude of your choice from the list that appears. Alternatively, you can click 
to create a new amplitude. (See Chapter 57, “The Amplitude toolset,” for more information.)
Note: The Amplitude field is unavailable if you are creating the boundary condition in the initial step (in which case the magnitude is always zero) or are fixing the magnitude at its final value from the previous general step (such as when editing a frequency step).
Click OK to save your data and to exit the editor.
