# Laplacian of a TensorField ?

 Register Blogs Members List Search Today's Posts Mark Forums Read

 September 23, 2010, 07:11 Laplacian of a TensorField ? #1 Senior Member   Join Date: Sep 2010 Location: France Posts: 224 Rep Power: 9 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
Super Moderator

Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
Posts: 693
Rep Power: 22
Quote:
 Originally Posted by T.D. solve ( fvm::ddt(c) + fvm::div(phi,c) == fvm::laplacian(A,T) );
so what you are saying is
Code:
`scalar + scalar == tensor`
I hope you see the mistake here

 September 23, 2010, 08:02 Hi #3 Senior Member   Join Date: Sep 2010 Location: France Posts: 224 Rep Power: 9 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
Super Moderator

Niklas Nordin
Join Date: Mar 2009
Location: Stockholm, Sweden
Posts: 693
Rep Power: 22
Quote:
 Originally Posted by T.D. ∇·(A*(∇.T))
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 Senior Member   Join Date: Sep 2010 Location: France Posts: 224 Rep Power: 9 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 Super Moderator     Niklas Nordin Join Date: Mar 2009 Location: Stockholm, Sweden Posts: 693 Rep Power: 22 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 exp-function can give you problems. if you are using 1.7.1 it is in OpenFoam-1.7.1/etc/controlDict lookup the line dimensionSet 1; and change the 1 to 0.

 September 23, 2010, 12:40 Thanks #7 Senior Member   Join Date: Sep 2010 Location: France Posts: 224 Rep Power: 9 Thanks a lot Niklas

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post mlawson OpenFOAM Running, Solving & CFD 18 May 21, 2017 08:15 OFCrash OpenFOAM Running, Solving & CFD 1 February 1, 2010 08:32 novyno OpenFOAM 1 November 23, 2009 20:31 Bedotto OpenFOAM Programming & Development 4 September 7, 2009 15:08 sven OpenFOAM 3 July 19, 2009 18:18

All times are GMT -4. The time now is 02:34.