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-   -   Solve Coupled Equations (http://www.cfd-online.com/Forums/openfoam-solving/58344-solve-coupled-equations.html)

nandiganavishal November 12, 2008 01:08

Hi I would like to solve c
 
Hi

I would like to solve coupled equations (using relaxation or Newtons method, but first would like to see for relaxation method). Can you help me which tutorial or solver should i follow in order to solve this problem.

Further I have solved a poisson equation adding source terms that are functions of x and y successfully. I had incorporated Dirichlet B.C's for a square 1*1 block (the b.c's are also functions of x and y). May I know how do we incorporate neumann b.cs for the same problem (they are also functions of x and y).

Say the four sides are inlet,outlet, upperwall and lowerwall.

My B.C's are

inlet (AT x =0) - Dirichlet B.C's = (y*(1-y)) (something of this
type).
Similarly (at y=0) (lowerwall) = -x^3 + sin (x)..

Neumann B.C's at x =1 (outlet) = -3-2*sin(x)(some arbitary function)
Neumann B.C's at y =1 (upperwall) = 4+sin(y)

For the inlet case I have my B.C statements like these... Which works fine..
label inletPatchID = mesh.boundaryMesh().findPatchID("inlet");
fvPatchScalarField& inletT = T.boundaryField()[inletPatchID];
const vectorField& faceCentresInlet =
mesh.Cf().boundaryField()[inletPatchID];
forAll(inletT, pointI)
{
inletT[pointI] = faceCentresInlet[pointI].y()*(1.0 -
faceCentresInlet[pointI].y());
}

Can anyone let me know how do we incorporate the neumann b.cs for this problem..

Kindly help me out..

Regards

Vishal

nandiganavishal November 12, 2008 23:47

Hi, I need to solve a coupl
 
Hi,

I need to solve a coupled equation which is of the form
laplacian(phi) = K * (C1-C2) ( K is some constant)
ddt(C1) = laplacian (phi,C1)+ extra terms;
ddt(C2) = laplacian(phi,C2)+ extra terms;

Could anyone let me know how exactly should i got go about solving this equation. Basically i want to solve a PNP equation, and I don't want it to be solved using relaxation method, I want to solve it using a single matrix (using some newton method or any other iteration techniques).

Can anyone throw some light with regard to this, as to what example i have to follow and how I should go about doing this.

Kindly help.

Thanks

Vishal


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