Average Pressure
The Average Pressure condition can be used to specify the pressure level. If it is not possible to specify the pressure level using a boundary condition, the pressure level must be set in some other way, for example, by specifying an average pressure in all flow domains.
Average Pressure Constraint
The relative average pressure is set by specifying the Average pressure pave. If the reference pressure pref defined at the physics interface level is equal to zero, pave represents the average absolute pressure.
When Include gravity and Use reduced pressure are selected, the average reduced pressure is constrained to pave.
The Average Pressure constraint couples all the degrees of freedom for the pressure. This could lead to large memory usage and ill-conditioned systems. In such cases, consider using a Pressure Point Constraint instead.