Use the Pressure node to specify the pressure on a boundary. In many cases the distribution of pressure is known, giving a Dirichlet condition
p =
p0 where
p0 is a known pressure given as a number, a distribution, or an expression involving time,
t, for example.
Enter a value or expression for the Pressure p0(SI unit: Pa). Enter a relative pressure value in
p0 (SI unit: Pa).
For the Subsurface Flow Module, the Pressure node provides the pressure
P0 as a condition on edges in 3D models. Then select the edges under
Edge Selection.