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-   -   problems with VERY simple mesh (http://www.cfd-online.com/Forums/fluent/42583-problems-very-simple-mesh.html)

Ralf Schmidt October 17, 2006 01:21

problems with VERY simple mesh
 
Hi!

I have a very simple mesh in gambit (2D, about 5000 tri cells, only 10 cells with an equiSize Skew higer than 0.22).

Now, exporting to and importing in Fluent is no problem. Performing a grid check is ok as well. Now, I turned the solver to axissymmetric and activate k-epsilon modell. After that, a new grid chek failed:

WARNING: non-positive volumes exist.

Waht happend???

ANY idea??

Ralf

mAx October 17, 2006 01:24

Re: problems with VERY simple mesh
 
check if your revolution axis is absolute coincident with your x-axis

Claud October 17, 2006 01:35

Re: problems with VERY simple mesh
 
and it should be only in positive direction on both axis.

Ralf Schmidt October 17, 2006 01:37

Re: problems with VERY simple mesh
 
Hi, thx for answer...

that might be the problem, but: First, I had the axis BC parallel to the y-axis, now it is coincident to the x-axis. But the problem still appears when i turn on the axis-symmetric solver.

Ralf


Ralf Schmidt October 17, 2006 01:45

Re: problems with VERY simple mesh
 
it is, but that doen't help...

mAx October 17, 2006 02:33

Re: problems with VERY simple mesh
 
check if the revolution axis lie exactly on the x-axis. a small gap about 1e-3 under the x-axis will crash the grid check

Ralf Schmidt October 17, 2006 05:54

problem solved!
 
Hi!

in the domain extents it is visible: the y domain starts from -1.2 e-14 - so there are some nodes below the x-axis!!

I solved the problem - editing the msh file: exchanging all y values below 0 to 0. Another way: translating the whole mesh in y-direction.

It works fine now... but why does fluent (or gambit) produces that problem???

Ralf

sach October 17, 2006 07:21

Re: problems with VERY simple mesh
 
hey have you checked right handed ness or left handed ness problem


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