[LateinCecker]

Hello Everyone,


i have recently gotten into CFD and i have been exploring the OpenFOAM source code a bit to better understand whats going on. Specifically, i have been looking into the incompressible/pimpleFoam and the compressible/rhoPimpleFoam solvers and i think by now i have a farely good grasp at what most of the code does. But there is one thing that strikes me as odd in the pressure equation sections of both solvers (pEqn.H):


After the pressure equation is solved, in the last non-orthogonal corrector loop the conservative flux

phi

is corrected. For the incompressible solver (pimpleFoam/pEqn.H) the corresponding code looks like this:

phi = phiHbyA - pEqn.flux();

which, from what i understand is equivalent to





and becomes





where the surface element [math] S = \Delta + k [\math]. This is all good and i get where it is coming from. The problem lies in the comparison to the compressible solver (rhoPimpleFoam/pEqn.H):


Here, the correction to the conservative flux is written as

phi = phiHbyA + pEqn.flux();

so the sign of the

 pEqn.flux()

is flipped. As i understand it, the

.flux()

function should be functionally identical to the incompressible case, except that now the density is a factor:








So if these equations are correct, then why is the sign for

pEqn.flux()

flipped in the compressible solver?




I hope this is the right forum for this question. Thx already in advance