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#1 |
New Member
Algis Dziugys
Join Date: Apr 2015
Posts: 10
Rep Power: 11 ![]() |
Hi,
I need to change conditionally fvVectorMatrix (UEqn for example) independently on fvOptions. For example, can I do like that: Foam::fvVectorMatrix UEqn ( Foam::fvm::div(phi, U) - Foam::fvm::laplacian(nu, U) == fvOptions(U) ); if(f_include_turbulence) UEqn += Foam::turbulence->divDevReff(U); if(f_include_gravity) UEqn -= g; UEqn().relax(); Or in other words, how do "-=" and "+=" work for fvVectorMatrix, what rules are? How to be sure that operators "-=" and "+=" will change UEqn.A or UEqn.H, or rhs? Thanks in advance. Last edited by Algis; November 7, 2015 at 16:24. |
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#2 |
Senior Member
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Hi,
it depends on rhs of += or -= operator. Since UEqn is fvVectorMatrix, look for meaning of operators, for example, at http://foam.sourceforge.net/docs/cpp...31bccd419a176b. Basically you are able to add another matrix, so it will be sum of matrices, or you can add volume field, in this case field will be added to equation source term. |
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#3 |
New Member
Algis Dziugys
Join Date: Apr 2015
Posts: 10
Rep Power: 11 ![]() |
Hi,
I did an experiment. Add gravity (defined as uniformDimensionedVectorField g) by two ways: 1) in definition of UEqn and 2) after definition of UEqn: 1) fvVectorMatrix UEqn_1 ( fvm::ddt(U) fvm::div(phi, U) - fvm::laplacian(nu, U) == -g ); 2) fvVectorMatrix UEqn_2 ( fvm::ddt(U) fvm::div(phi, U) - fvm::laplacian(nu, U) ); UEqn_2 -= g; and then compared both UEqn_1 and UEqn_2. The result was that A(), H1, source() and residual() were the same for UEqn_1 and UEqn_2, while H() was different. Why H() was different? Thank you very much in advance, Algis |
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#4 |
Member
Mattia de\' Michieli Vitturi
Join Date: Mar 2009
Posts: 51
Rep Power: 17 ![]() |
Hi Algis,
please can you try with: UEqn_2 += g; Ciao Mattia |
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#5 |
New Member
Algis Dziugys
Join Date: Apr 2015
Posts: 10
Rep Power: 11 ![]() |
Hi Mattia,
I did it and now there is no difference in H() and others. So, analog of fvVectorMatrix UEqn ( fvm::ddt(U) fvm::div(phi, U) - fvm::laplacian(nu, U) == -g ); is fvVectorMatrix UEqn_2 ( fvm::ddt(U) fvm::div(phi, U) - fvm::laplacian(nu, U) ); UEqn_2 += g; but not "UEqn_2 -= g"; Thanks Mattia, now I see in what was my misunderstanding. Best regards, Algis |
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fvvectormatrix |
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