[Jasper Z]

Dear all,

I want to know what does the momentum source function return when we call it which is defined in KinematicCloudI.H:

template<class CloudType>
 inline Foam::tmp<Foam::fvVectorMatrix>
 Foam::KinematicCloud<CloudType>::SU(volVectorField& U, bool incompressible)
 const
 {
     if (debug)
     {
         Pout<< "UTrans min/max = " << min(UTrans()).value() << ", "
             << max(UTrans()).value() << nl
             << "UCoeff min/max = " << min(UCoeff()).value() << ", "
             << max(UCoeff()).value() << endl;
     }
  
     dimensionSet dim(dimForce);
     if (incompressible)
     {
         dim.reset(dimForce/dimDensity);
     }
  
     if (solution_.coupled())
     {
         if (solution_.semiImplicit("U"))
         {
             volScalarField::Internal
                 Vdt(mesh_.V()*this->db().time().deltaT());
  
             if (incompressible)
             {
                 Vdt.dimensions() *= dimDensity;
             }
  
             return UTrans()/Vdt - fvm::Sp(UCoeff()/Vdt, U) + UCoeff()/Vdt*U;
         }
         else
         {
             tmp<fvVectorMatrix> tfvm(new fvVectorMatrix(U, dim));
             fvVectorMatrix& fvm = tfvm.ref();
  
             fvm.source() = -UTrans()/(this->db().time().deltaT());
  
             return tfvm;
         }
     }
  
     return tmp<fvVectorMatrix>::New(U, dim);
 }

If I use semiImplicit, does it return

UTrans()/Vdt - fvm::Sp(UCoeff()/Vdt, U) + UCoeff()/Vdt*U

or

tmp<fvVectorMatrix>::New(U, dim)

?
I think the code returns the latter, so what does

tmp<fvVectorMatrix>::New(U, dim)

mean?

Kind regards,
Jasper