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-   -   When and how to apply nonOrthogonal correctors (http://www.cfd-online.com/Forums/openfoam-solving/60277-when-how-apply-nonorthogonal-correctors.html)

vvqf March 21, 2006 07:14

to help get a better faster co
 
to help get a better faster convergent solution.

Hi dear all,

i read some posts and got an impression:
- generally in simpleFoam better no use of nonOrthogonal correctors. in case the mesh is bad, and after many tries solution still diverges, try better 1 nonOrthogonal corrector. But it wont always help.

- with PISO algorithm, we can consider using nonOrthogonal correctors, but be carefull, since it uses too much resouce and time to compute.

- it depends on the mesh quality, and cell type, hexahedral, prismsm or tetrahedral or mixed. Even with well meshed hexahedral cells, we can think about applying nonOrthogonal correctors?
How many nonOrthogonal correctors to use properly?
how to judge from the checkMesh message? :
for example:

Max cell openness = 6.93889e-18 Max aspect ratio = 44.749. All cells OK.

Minumum face area = 6.04474e-08. Maximum face area = 0.0379173. Face area magnitudes OK.

Min volume = 5.93429e-11. Max volume = 0.0024023. Total volume = 12.1388. Cell volumes OK.

Mesh non-orthogonality Max: 62.463 average: 10.9583
Non-orthogonality check OK.


Face pyramids OK.

Max skewness = 65.1704 percent. Face skewness OK.

Minumum edge length = 7.40051e-05. Maximum edge length = 0.208085.


related:
http://www.cfd-online.com/OpenFOAM_D...es/1/1075.html

vvqf March 22, 2006 06:21

for my 'simpleFoam' computatio
 
for my 'simpleFoam' computation
- the mesh is all Hexa with the above checkMesh message
- 1000 iterations.
- default fvSchemes.
- reduced relaxation factors on p, k and epsilon
it always diverges, fast.

then 1 nonOrthogonal corrector was set and same time relaxation factors for k and epsilon were lowered to 0.2(not sure if it's enough).
it still diverged, but slowly.

i am not sure whether it is the 1 nonOrthogonal corrector helped.

later I want to use other fvSchemes.


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