[AndreaCFD]

Dear members,

I am new to OpenFoam and I am trying to modify the icoFoam solver to export the matrix of coefficients UEqn into a text file readable by Matlab.

What is the easiest way? I am really new to C++ too and I can't compile the solver without errors. May you help?

Thanks in advance,

Andrea

[olesen]

Originally Posted by AndreaCFD

Dear members,

I am new to OpenFoam and I am trying to modify the icoFoam solver to export the matrix of coefficients UEqn into a text file readable by Matlab.

What is the easiest way? I am really new to C++ too and I can't compile the solver without errors. May you help?

Thanks in advance,

Andrea

Changing any solver to simply dump out a matrix of coefficients is really not a good idea. It falls apart when you want to try the same for a different field, for a slightly different solver, or when you upgrade versions. Provided that you do not yet wish to examine the coefficients for the pressure equation, you can implement your writing routine as a matrix constraint that does not modify the coefficients, but only prints them out. If you are new to OpenFOAM and to C++, it will not be completely easy in any case. You need to walk the OpenFOAM sparse matrix storage, and also handle processor-to-processor connections.

If you want a bit of code to start from, I have revived some old code (temporarily?) that probably does most of what you want, or at least can give you some ideas. It dumps coefficients in a MatrixMarket format. Although it is from 2018, it should compile OK with OpenFOAM-v1906,1912,2006. I cannot remember if there is anything missing or broken in it.


https://develop.openfoam.com/modules...src/dumpMatrix

[anhkenyt]

Originally Posted by AndreaCFD

Dear members,

I am new to OpenFoam and I am trying to modify the icoFoam solver to export the matrix of coefficients UEqn into a text file readable by Matlab.

What is the easiest way? I am really new to C++ too and I can't compile the solver without errors. May you help?

Thanks in advance,

Andrea

Hi Andrea,
To start, the document below will give you some simple suggestions
https://www.foamacademy.com/wp-conte...2018matrix.pdf

[AndreaCFD]

Originally Posted by anhkenyt

Hi Andrea,
To start, the document below will give you some simple suggestions
https://www.foamacademy.com/wp-conte...2018matrix.pdf

Dear Van Duc Anh,

thanks for the useful documentation. I tried to write the code as follows:

fvVectorMatrix UEqn
        (
			fvm::laplacian(nu, U)-
			fvm::div(phi_zero, U)-
			fvc::div(phi,U_zero)
        );

		
		label NC = mesh.nCells(); //Number of cells
		simpleMatrix<scalar> A(NC); //Coeff.matrix

		// Initialization of matrix
		for(label i=0; i<NC; i++)
			{
				A.source()[i] = 0.0;
				for(label j=0; j<NC; j++)
					{
						A[i][j] = 0.0;
					}
			}
	
		// Assigning diagonal coefficients
		for(label i=0; i<NC; i++)
			{
				A[i][i] = UEqn.diag()[i];
			}
	
		// Assigning off-diagonal coefficients
		for(label faceI=0; faceI<UEqn.lduAddr().lowerAddr().size(); faceI++)
			{
				label l = UEqn.lduAddr().lowerAddr()[faceI];
				label u = UEqn.lduAddr().upperAddr()[faceI];
				A[l][u] = UEqn.upper()[faceI];
				A[u][l] = UEqn.upper()[faceI];
			}
		// Assigning contribution from BC
		forAll(U.boundaryField(), patchI)
			{
				const fvPatch &pp = U.boundaryField()[patchI].patch();
				forAll(pp, faceI)
					{
						label cellI = pp.faceCells()[faceI];
						A[cellI][cellI] += UEqn.internalCoeffs()[patchI][faceI];
						A.source()[cellI] += UEqn.boundaryCoeffs()[patchI][faceI];
					}
			}
	
		Info << "\n==Coefficients of Matrix A=="<< endl;
		for(label i=0; i<NC; i++)
			{
				for(label j=0; j<NC; j++)
					{
						Info<< A[i][j] << " ";
					}
				Info<< A.source()[i] << endl;
			}

But I get an error I am not able to understand:

[/CODE] error: no match for ‘operator+=’ (operand types are ‘double’ and ‘Foam::Vector<double>’)
A[cellI][cellI] += UEqn.internalCoeffs()[patchI][faceI]; [/CODE]

How do I overcome it?
Thanks in Advance

Andrea

[dlahaye]

https://openfoamwiki.net/images/1/18/GdbOF-Manual.pdf

[TommyJ]

@Mr. Olesen, The link you provided is broken. Was there a problem with the code?

@Mr. Lahaye, can gdbOf print the coefficients in a parallel run?

[dlahaye]

@tommyJ: not sure.

Possibly yes: gdb seems to support parallel runs.

Possibly no: in parallel, OpenFoam stores the matrix per processor in separate (diagonal and off-diagonal blocks), and the macros provided in OFgdb might not extend to this situation. Possibly OFgdb can be extended to treat this case.