# Problem to solve ddt(U)+laplacian(nu,U)=f

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 February 9, 2014, 08:44 Problem to solve ddt(U)+laplacian(nu,U)=f #1 Member   Join Date: Feb 2012 Posts: 49 Rep Power: 5 I'm going to solve the below equation where U is the velocity field and f is a volume vector field with the dimension of m/s^2. fvVectorMatrix UEqn fvm::ddt(U)- fvm::laplacian(nu, U)+f By using a solver like 'PBiCG' i get the error that i need a symmetric matrix solver. After choosing a symmetric solver, i get the error that : keyword agglomerator is undefined in dictionary From function dictionary::lookupEntry(const word&, bool, bool) const in file db/dictionary/dictionary.C at line 402. And when i use an implicit approach ( fvm::Sp(1,f) ) instead of 'f' , i get another error about incompatibility of f and U. I would appreciate if somebody can tell what is wrong here.

 February 10, 2014, 04:35 #2 Senior Member     Anton Kidess Join Date: May 2009 Location: Delft, Netherlands Posts: 919 Rep Power: 17 You didn't choose 'a' symmetric solver as in an arbitrary one, but specifically GAMG, right? And then you get the error "keyword agglomerator is undefined in dictionary". May I suggest adding that keyword to your solution dictionary? ooo likes this. __________________ *On twitter @akidTwit *Spend as much time formulating your questions as you expect people to spend on their answer. *Help define the OpenFOAM stackexchange Q&A site: http://area51.stackexchange.com/prop...oam-technology

February 10, 2014, 07:14
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Quote:
 Originally Posted by akidess You didn't choose 'a' symmetric solver as in an arbitrary one, but specifically GAMG, right? And then you get the error "keyword agglomerator is undefined in dictionary". May I suggest adding that keyword to your solution dictionary?
Thank you very much, it works.
Always i thought there is a problem in my code,So not concentrated on somewhere else! Thanks.

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