[Dmitiy]

Hello everyone.
I'm trying to implement functionality similar to scalarTransport function object directly in interFoam solver in order to be able to correct implemented equations manually in the future. As a starting point I decided to dig into the scalarTransport.C source code. In a part of this file related to two-phase scalar transport one can see:

// Two phase scalar transport
     if (phaseName_ != "none")
     {
         const volScalarField& alpha =
             mesh_.lookupObject<volScalarField>(phaseName_);
  
         const surfaceScalarField& limitedPhiAlpha =
             mesh_.lookupObject<surfaceScalarField>(phasePhiCompressedName_);
  
         D *= pos(alpha - 0.99);
  
         // Reset D dimensions consistent with limitedPhiAlpha
         D.dimensions().reset(limitedPhiAlpha.dimensions()/dimLength);
  
         // Solve
         tmp<surfaceScalarField> tTPhiUD;
         for (label i = 0; i <= nCorr_; i++)
         {
             fvScalarMatrix sEqn
             (
                 fvm::ddt(s)
               + fvm::div(limitedPhiAlpha, s, divScheme)
               - fvm::laplacian(D, s, laplacianScheme)
               ==
                 alpha*fvOptions_(s)
             );
  
             sEqn.relax(relaxCoeff);
             fvOptions_.constrain(sEqn);
             sEqn.solve(mesh_.solverDict(schemesField_));
  
             tTPhiUD = sEqn.flux();
         }

So the questions are:

1) Did I understand correctly, that limitedPhiAlpha in case of interFoam solver stays for alphaPhi10 flux?
2) What is the function of

fvOptions_.constrain(sEqn);

before solve() method and where can I find description of it?

Thank you in advance.

[randolph]

limitedPhiAlpha in interFoam is alphaPhiUn