The Outlet node adds a boundary condition for the outflow perpendicular (normal) to the boundary:

where Dc is the capillary diffusion (SI unit: m2/s) and c1 = s1ρ1 is the fluid 1 content (SI unit: kg/m3). This means that the normal gradient of fluid saturation does not change through this boundary.

Enter a value or expression for the Pressure p. The default value is 0. If the reference pressure pref, defined at the physics interface level is 0, enter the absolute pressure. Otherwise, enter the relative pressure.