Solving an equation implicitely

fshak92 · October 13, 2014, 05:36

Hi FOAMers,

I would like to solve this equation :

laplacian(U) + U = (known field)

where u is unknown volVectorField and should be solve implicitly.
i don't know what i can do with the term (U), because to solve the equation implicitly i can write:

Code:

solve ( fvm::laplacian(U) + fvm::U == knownTerm...)

The problem is that the term fvm::U does not work because i need an operator after fvm::, and if i just write (U), OpenFOAM uses the value from the previous time step, which will be different from what i'm going to solve...
Does anybody know how i can deal with the U term to solve it implicitly?
Tnx,

ahmmedshakil · October 13, 2014, 05:48

Have you tried with:
fvm::Sp(1,U) ?
(term I have written for example)

#shakil

October 13, 2014, 05:36	Solving an equation implicitely	#1
fshak92 Senior Member Join Date: Dec 2011 Posts: 121 Rep Power: 14	Hi FOAMers, I would like to solve this equation : laplacian(U) + U = (known field) where u is unknown volVectorField and should be solve implicitly. i don't know what i can do with the term (U), because to solve the equation implicitly i can write: Code: solve ( fvm::laplacian(U) + fvm::U == knownTerm...) The problem is that the term fvm::U does not work because i need an operator after fvm::, and if i just write (U), OpenFOAM uses the value from the previous time step, which will be different from what i'm going to solve... Does anybody know how i can deal with the U term to solve it implicitly? Tnx,

October 13, 2014, 05:48		#2
ahmmedshakil Senior Member Mohammad Shakil Ahmmed Join Date: Oct 2012 Location: AUS Posts: 137 Rep Power: 14	Have you tried with: fvm::Sp(1,U) ? (term I have written for example) #shakil fshak92 likes this.

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