multiphase explicitsolve function in interFoam
 

hello all
I am trying to couple volume of fluid with level set in interFoam (2.3.0). For this purpose, I have to solve this PDE for artificial time not phyiscal time.

ddt(psi) + div.(psi *(1 - psi ) n) = div.(epsilon * (grad(psi) * n) n)

where psi : is level set
n : is the normal to the interface and is already calculated by interFoam
epsilon : is a parameter related to the mesh size (dx/2 )
I thought of using subcycle used in interFoam.
the second term in the left hand side can be hendled by
fvc::flux
(
-fvc::flux(-phisf, scalar(1.0) - psi ,psiScheme) ,
psi ,
psiScheme
)
where phisf is the normal flux which is the same as interface.nHatf()

now I have a problem with handling with the right hand side because of grad term. So could you guys please gives me hand to handle such a term as flux in order to use it in explicitSolve function. Thanks alot .