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September 23, 2010, 07:11 
Laplacian of a TensorField ?

#1 
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Hi,
How to calculate laplacian of A*T if A is a scalar function of another scalar Main field c and , T is a 2nd order tensor example when i put " solve ( fvm::ddt(c) + fvm::div(phi,c) == fvm::laplacian(A,T) ); A=2*pow(c,2)+5; " it doesnot work!!!!? Help lease?? 

September 23, 2010, 07:18 

#2 
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Niklas Nordin
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September 23, 2010, 08:02 
Hi

#3 
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Execuse me,
In another words the last term to the write is ∇·(A*(∇.T)) which must be a scalar ok to go on with the c equation. where A is a scalar and T is a second order tensor so ∇·T is div(T) and it is a vector ok (since divergence of a tensor) ?? and V=A*∇·T is a vector then so ∇·(A*(∇.T)) must be written something like div(A,V) ?? knowing that A is always a function of c. helpme Thanks 

September 23, 2010, 08:14 

#4 
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Niklas Nordin
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ah ok, so its 2 div operations...
∇·(A*(∇.T)) = fvc::div(A*fvc::div(T)) but this will make this term fully explicit. I think it will be hard to treat it fully implicit. If you run into stability problems you should try to split it up into implicit/explicit parts. 

September 23, 2010, 09:43 
HI

#5 
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Hi Niklas thanks,
BUT A is a function of the scalar field c. so it stays like that ∇·(A*(∇.T)) = fvc::div(A*fvc::div(T)) ?? another thing please: do you know how to turn off all dimensions? thank you so much 

September 23, 2010, 09:54 

#6 
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Niklas Nordin
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yes of course it does.
and why do you want to turn off dimensions, it has saved me on numerous occasions. but ok, I can see that the expfunction can give you problems. if you are using 1.7.1 it is in OpenFoam1.7.1/etc/controlDict lookup the line dimensionSet 1; and change the 1 to 0. 

September 23, 2010, 12:40 
Thanks

#7 
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Thanks a lot Niklas


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