[Andrea_85]

Hi All,

i am using interFoam and i would like to evaluate separately the contribution of each term of the momentum equation at the end of each time-step. The first thing i am trying to check (to be sure i am calculating them correctly) if the most obvious one: if all the terms of the equation sum up to zero (or at least to something very small), but...surprisingly...they don't. What i did is:

at the end of the pressure loop, just before the runTime.write() is called, i added:

volVectorField sumNS = fvc::ddt(rho,U) + fvc::div(rhoPhi,U) + fvc::grad(p_rgh) - fvc::laplacian(muEff, U) -(fvc::grad(U) & fvc::grad(muEff)) - interface.sigmaK()*fvc::grad(alpha1);

and then i took the volume integral of this quantity (summing up over all the cells). The results is not zero, neither something small.

What i am not sure is if i am calculating all the contributions in a way that is consistent with predictor-corrector step in interFoam or maybe i just missed something in the definition of "sumNS" (gravity is set to zero, that's why the term ghf*fvc::snGrad(rho) is missing and the pressure gradient is calculated with p_rgh; also the simulation is laminar).

So, should i expect a result different from zero if i calculate explicitly the sum of all the terms of the equation?...i hope the answer is no...
So what i am doing wrong?

Best,

Andrea