# How should I implement this scalar transport equation

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 April 14, 2014, 09:38 How should I implement this scalar transport equation #1 Senior Member   Dongyue Li Join Date: Jun 2012 Location: Torino, Italy Posts: 754 Rep Power: 10 Hi guys, I wanna solve this equation: I code it like this: Code:  fvScalarMatrix nEqn ( fvm::ddt(j) + fvm::div(phi1,j) == C1*j* epsilon -fvm::Sp(C2*pow(j, 2.0/9.0)* epsilon, j) ); But it's result is wired. Thanks in advance. Last edited by sharonyue; April 14, 2014 at 21:55.

 April 14, 2014, 21:32 #2 Member   xuhe-openfoam Join Date: Aug 2013 Location: DaLian，china Posts: 82 Rep Power: 6 hello! maybe you could give more information , for example: C1>0 or C1<0, epsilon?

April 14, 2014, 21:37
#3
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Dongyue Li
Join Date: Jun 2012
Location: Torino, Italy
Posts: 754
Rep Power: 10
Quote:
 Originally Posted by bieshuxuhe hello! maybe you could give more information , for example: C1>0 or C1<0, epsilon?
C1, C2, epsilon is all positive~ can I deal with this with some sophisticated approach?

 April 14, 2014, 22:53 #4 Member   xuhe-openfoam Join Date: Aug 2013 Location: DaLian，china Posts: 82 Rep Power: 6 I suppose that : 1 "j+jSmall" is "j" 2 there is no limit of the value of "j" then , modify the source term " -C2*pow((j+jSmall),11.0/9.0)* epsilon " to : Code: - 11.0/9.0*C2*fvm::Sp(epsilon,j) + 2.0/9.0*C2*epsilon*pow(j,11.0/9.0) maybe this will be fine! of cource maybe there is some other reason for wired result, not only the discretization of source term.

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