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-   -   Dimension problem (http://www.cfd-online.com/Forums/openfoam-solving/59121-dimension-problem.html)

faroque November 24, 2006 21:25

I am getting the following err
 
I am getting the following error.

-----------------------------------------------
--> FOAM FATAL ERROR : incompatible dimensions for operation
[U[0 1 -1 0 0 0 0] ] - [U[0 -1 0 0 0 0 0] ]

From function checkMethod(const fvMatrix<type>&, const fvMatrix<type>&)
in file /home/faroque/OpenFOAM/OpenFOAM-1.3/src/finiteVolume/lnInclude/fvMatrix.C at line 1024.

FOAM aborting

Foam::error::printStack(Foam:http://www.cfd-online.com/OpenFOAM_D...part/proud.gifstream&)
Foam::error::abort()
./newApp [0x80525e5]
./newApp [0x8061e31]
./newApp [0x804f354]
__libc_start_main
__gxx_personality_v0
0Aborted
---------------------------------------------
It seem to me problem in the dimension defition for my volScalarField variable. I defined variable dimension like follwoing:

dimension [0 0 0 1 0 0 0]

Could someone help me?

hjasak November 24, 2006 21:29

Your error says the simulation
 
Your error says the simulation has failed in the momentum equation - one of the terms you've added has got wrong dimensions.

Hrv

faroque November 24, 2006 21:56

Thanks for the reply. I have
 
Thanks for the reply.
I have set the equation in following way..

-------------------------------------------------
solve
(
fvm::ddt(T) == fvm::laplacian(T)
);
--------------------------------------------------
where T is a volScalarField. Did I make any mistake here?

--
Faroque

stephan November 25, 2006 10:20

Hi, there should be a trans
 
Hi,

there should be a transportcoefficient for temperatur in this kind of equation?!
sth like: a*ddt(T)=laplaceian(T),where a is sth like
rho*c/lambda.
otherwise your dimensions are K/s on the left side and K/m^2 on the right side.
for the value of the transport coefficient you should look i a textbook to find something for your material...
stephan

amagda November 26, 2006 07:39

hi, if u want to use the e
 
hi,

if u want to use the equation like that the code should looke like:

solve
(
fvm::ddt(T) - fvm::laplacian(
dimensionedScalar
(
"scal", dimensionSet(0, 2, -1, 0, 0), 1),
T)
);
}

Actually u just multiply with a scalar with unit value 1[m2/s]

Adrian

johndeas February 19, 2008 09:56

Isn't there a way to tell the
 
Isn't there a way to tell the solver that space and time variables used for the derivation are dimensionless ?


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