[MarcusAng]

Hi everyone,

I am having trouble understanding p_rgh and p results for interFoam.

Consider the tutorial case $FOAM_TUTORIALS/multiphase/interFoam/laminar/capillaryRise

From what I understand, p_rgh (Pa) is a modified pressure term that is defined such that it is more efficient to solve incompressible and compressible problems in multiphase flow. p_rgh term does not contain the hydrostatic pressure. On the other hand, p is the total gauge pressure (Pa) and should contain the hydrostatic pressure effects. Hydrostatic pressure w.r.t origin is rho*gh and therefore from the OpenFOAM documentation, the following equation is true
p' (i.e. p_rgh)=p-rho*gh

Now, if I want to submerge my capillary pipe initially (not fill up capillary tube), does it make sense to extend the capillary pipe in the negative z direction? And if so, does it make sense to still use p_rgh=0 as the inlet boundary condition?

Thanks,
Marcus