How to apply face pressures
Neumann boundary condition are applied using following conditions in KRATOS,
FACE2D(3D) or FACEPRESSURE2D(3D) in STRUCTURAL application Fluid3DNeumann or Monolithic2DNeumann(and 3D) in INCOMPRESSIBLE application.
All of them take external pressures, through variables like, EXTERNAL_PRESSURE, PRESSURE,NEGATIVE_FACE_PRESSURE and POSITIVE_FACE_PRESSURE, and then compute the NORMAL and apply the calculated forces on the nodes.
Fluid3DNeumann is written to work with Fractional step solvers while Monolithic2DNeumann is written to work with mixed u-p systems. The reader is supposed to have a look on these conditions and choose the one tha tis more appropriate to his/her needs.