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October 2, 2010, 11:48 
rho euation in rhoPisoFoam

#1  
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Nilesh Rane
Join Date: Apr 2010
Posts: 122
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Hi,
In rhoPisoFoam, the .c code includes rhoEqn.H file but the file is not in that folder. Is is getting included from some other common directory?? I am asking this because when i solve my simulation the rho equation is not getting solved, it seems. Can anyone tell me, what is the problem here?? Why the rho equation is not being solved?? Quote:
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October 3, 2010, 21:06 

#2 
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Alberto Passalacqua
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Search your OpenFOAM1.7.x/src directory for rhoEqn.H and you will find it. It is basically
solve(fvm::ddt(rho) + fvc::div(phi)); with explicit discretization of the divergence to avoid conservation errors. The fact you see residuals equal to zero means that the solution is exact, not that the equation is not solved. You are using the diagonal solver, which is direct, and gives you the exact solution of the linear system. Best,
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Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

October 4, 2010, 06:07 

#3 
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Nilesh Rane
Join Date: Apr 2010
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But No of iterations is also 0.
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October 4, 2010, 12:02 

#4 
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Alberto Passalacqua
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This is really basic
How many iterations do you need to obtain the exact solution of a linear system with a direct solver? The answer is zero, because the method is not iterative You basically can easily do that with the Thomas algorithm for whatever tridiagonal system (or block tridiagonal). Check a book on the topic to have the details. Best,
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Alberto Passalacqua GeekoCFD  A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats. OpenQBMM  An opensource implementation of quadraturebased moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using. 

October 5, 2010, 07:44 

#5 
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Nilesh Rane
Join Date: Apr 2010
Posts: 122
Rep Power: 8 
Ohh...OF takes it in that sense. I was thinking on different line. I thought if you solve an equation (or rather a system of equations in turn) 1 time then No of Iterations should be 1 and so on...
I do know about TDMA.. have used it in my UG assignments.. Thanks a lot..
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