[Democritus]

Hi Dear Foamers~!
I am trying to test a program by prescribing the dirichlet BCs and source terms which are all calculated from the prescribed exact solution:

fvScalarMatrix p1SinEquation
(
    fvm::Sp(1, p1) + fvc::div(v)
); // v is already known
solve( p1SinEquation == p1SourceTerm )

//impose the source term
p1SourceTerm = p1_Exact + fvc::div(v);
//impose the BC
const fvBoundaryMesh & meshBoundary = mesh.boundary();
  forAll( meshBoundary, fvPatchID )
  {
    const fvPatch & instantPatch = meshBoundary[ fvPatchID ];
    forAll( instantPatch, elmtID )
    {
      p1.boundaryField()[fvPatchID][elmtID]  
      = 
      p1_Exact.boundaryField()[fvPatchID][elmtID];
    }
  }

By this way I succecced in imposing the BC and source term, but after the calculation, the field p1's boundary value changes, which means that the fixed Dirichlet boundary conditions shifted. How to make it fixed firmly during all the program runtime?

I am open for all advices and thanks in advance!

[ssss]

You could create a variable inside the solver and create a custom boundary conditions using swak4foam or codexFixed custom BC

[Democritus]

Originally Posted by ssss

You could create a variable inside the solver and create a custom boundary conditions using swak4foam or codexFixed custom BC

Thank you! I am trying my best to implement a new BC on the base of fixed value BC.

[Tobi]

Use swak4Foam and live gets so easy

[Zhiheng Wang]

Hi Tobi,
I am facing problem to write grrovy BC while the Boundary Condition is coupled/mapped of 0/T and 0/U , can I write a coupled or mapped boundary I have tried by Code stream but it was a disaster.
U=(diff*(gradYi)/(1-Yi))
and

gradT= rho*U*Hf/kappa Can i write this with groovy BC for inlet ???

[Tobi]

Yes you can use values from other patches and also map stuff.

[Zhiheng Wang]

Originally Posted by Tobi

Yes you can use values from other patches and also map stuff.

How to use map conditions ???? With groovy BC. I have no Idea about it.

[Democritus]

Hi Dear Foamers~

Here I want to share my solution about this issue. I only use OpenFOAM in order to impose a BC. The field I want to deal is pS, pC, vS, vC.

First I implemented codes for imposing the BC

    const fvBoundaryMesh & thisBoundary = mesh.boundary(); //here I get the boundary of the mesh
    forAll( thisBoundary, fvPatchID ) // go through all the patchs of the boundary
    {
      const fvPatch & thisPatch = thisBoundary[ fvPatchID ];
      Info << "\n Imposing the boundary condition on the fvPatch of " <<
      thisPatch.name() << endl;

      const vectorField & position = thisPatch.Cf(); // get the cell face centers' positions
      forAll( thisPatch, elmtID ) // imposing values on the centers of all the cell faces of this patch   
      {
        const scalar & x = position[elmtID].component(0);
        const scalar & y = position[elmtID].component(1);

        //you can replace your function on the right side of the =
        pS.boundaryField()[fvPatchID][elmtID] = -1 * Foam::exp(-1 * x) * Foam::cos( x );
        pC.boundaryField()[fvPatchID][elmtID] = Foam::exp(-1 * x) * Foam::sin( x );

        vS.boundaryField()[fvPatchID][elmtID].component(0) = -1 * Foam::exp(-1 * x) * Foam::cos( x );
        vS.boundaryField()[fvPatchID][elmtID].component(1) = 2 * Foam::cos( x ) * Foam::sin( y ) ;

        vC.boundaryField()[fvPatchID][elmtID].component(0) = Foam::exp(-1 * x) * Foam::sin( x );
        vC.boundaryField()[fvPatchID][elmtID].component(1) = Foam::sin( x ) * Foam::cos( y );

      }

    }

Then I writed these fileds into files. In the files I changed the BC type from "calculated" to "fixedValue". Then I copy these files into the cases that I want to use it.

As old saying in China goes, "抛砖引玉", which means "showing a brick on the market in order to motivate others to show sapphire on the market", here I post my solution for dear foamers' reference and I am always open for any advice of improvement.
Thanks!