[luckycfd]

Hello all,
According to the reference that it's address link is below, in page 53;
http://www.diva-portal.org/smash/get...T01.pdf‎
I can,t undrestand that what is the placeholder matrix in openFoam? and how get this equations:

u(0)=[2,0] u(1)=[3,1] l(0)=[0,2] l(1)=[1,3]

UpperAddr=(2,3) LowerAddr=(0,1)

Best regards,
Hassan

[luckycfd]

can anyone explain the placeholder matrix in openfoam?

[Amiin]

Dear Hassan,

As far as I know, OF uses a LDU method to store large sparse matrixes to save memory. In your reference, A is a matrix which is stored as the sum of three matrixes.

1- Diagonal list which stores only diagonal elements.
2- Lower list for storing lower triangular elements, row wised from left to right.
3- Upper list for storing upper triangular elements, column wised from left to right.

Then for addressing these off-diagonal elements, since upper and lower elements are symmetric, only one of them are addressed.
E.g. upperAddr contains the rows of lower list elements and lowerAddr contains the column of them.
So for upper list elements, upperAddr is for columns and lowerAddr is for rows.

Regards,

Amin

[luckycfd]

Dear Amin,

thanks a lot

Best regadrs,
Hassan

[luckycfd]

Hi,
According to the:
http://openfoamwiki.net/index.php/Op...es_in_OpenFOAM
What is the "computational molecule" term in the Sentence below?
"OpenFOAM uses a small computational molecule, therefore only adjacent cells influence one another."

Best regards,
Hassan

[sharonyue]

Hi guys:

If the solver prints:

Lower triangle = 7(-0.05 -0 -0.05 -0 -0 -0.05 -0.05)

diagonal = 6(0.05 0.05 0 0.05 0.05 0)

Upper triangle = 7{0}

what does it mean?

if the diagonal coefficients are 6, is the upper and lower triangle coefficients should be (5+4+3+2+1)=15?

[luckycfd]

good question,
I don't know!

[Henning86]

if the matrix is symmetric, only the diagonal is stored to save RAM. can be seen in the ldumatrix class

[luckycfd]

Hi sharonyue,

How can get this output? access to the these lists in a special test case for example in cavity by icoFoam:

Lower triangle = 7(-0.05 -0 -0.05 -0 -0 -0.05 -0.05)  
diagonal = 6(0.05 0.05 0 0.05 0.05 0)  
Upper triangle = 7{0}

Regards,
Hassan

[j-avdeev]

Hello, luckycfd.

Probably matricoFoam will help you to understand:
http://www.cfd-online.com/Forums/ope...tml#post472905