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-   -   [GAMBIT] Problems while meshing a 3d CAD model (https://www.cfd-online.com/Forums/ansys-meshing/108972-problems-while-meshing-3d-cad-model.html)

-mAx- January 3, 2013 01:34

it is crashing for a specific operation.
Which one?
>> in your .jou, check the last line (operation)

Aadhavan January 3, 2013 03:55

hi,
while creating faces, its crashing.
Thanks,
Aadhavan

-mAx- January 3, 2013 04:07

1 Attachment(s)
although I am sceptic about creating volume like you are doing, try to create your surface with help other edges.
I assume it is referencing on the surface with 4 red edges in your pdf, so you can try to split the edge opposite to the dark red one (split it in the middle), and create an edge from this midpoint till opposite point (check green edge in picture) Attachment 17943
Then create both surfaces.

In your case I would create airfoils volume. Then your quarter volume (90° rotation).
Then substract this quarter with airfoils >> new volume has hollow in place of airfoils.
Finally do your volume decomposition with splits

Aadhavan January 3, 2013 04:25

hi,
I got what you are saying, thanks for your suggestion, I will do it for next case.
how ever I have done meshing by my approach, but OF takes more time.
for 12 hrs only 60 time step. Now I am running in one processor.

mAx, I have small question to you, what are the basic things we need to check while doing the simulation ( i,e tip speed, torque, pressure raise).
please give me some information.

Thanks,
Aadhavan

-mAx- January 3, 2013 04:40

-check Mesh
-check convergence
-monitoring any goal
-plausibility of your results (don't hesitate to break computation and check velocity/pressure dustribution)

Aadhavan January 3, 2013 04:46

thanks mAx, I have done check mesh. there is now error and warning message.

I am trying to run in parallel, I will update here.

Thanks,
Aadhavan

Aadhavan January 5, 2013 06:50

1 Attachment(s)
Hi mAx and others,
while executing the check mesh, it says:

Checking geometry...
Overall domain bounding box (-2.64119e-16 -2.64893e-16 -3) (0.771296 0.771367 7)

As mentioned before I am using Gambit for meshing. my geometry is quarter of the volume between two cylinders (see the image).

the inner cylinder radius is 0.3072m and outer cylinder radius id 0.771m
-z= 3m and +z = 7 m

I am wondering how can be the bounding box can have this dimension (-2.64119e-16 -2.64893e-16 -3)
is it a problem?

second one:

I ran my simulation for above geometry up to 1500 time step, then I checked the results. The results are totally wrong and the time step continuity error keep on increasing. I am not able to figure out the problem. if I change relTol=0 in fvSolution for p then there is no problem for time step continuity error, but its taking around 10 to 15 min per time step because its taking lot of time to solve p.
please guide me what to do.

please guys, if you are able to spare some time for this case please have a look. I am really dont know what to do.
I have uploaded my case here,
http://www.sendspace.com/file/zcqhmu


Thanks in advance,
Aadhavan

-mAx- January 7, 2013 01:10

if you are working with OpenFOAM, I would open a new thread in the OpenFOAM subforum. You will have more chance getting replies.
The e-16 are only tolerance "issues", so it is referecing to 0 --> in your case (0 0 -3)

Aadhavan January 7, 2013 01:52

Dear mAx,
Thanks for your reply, I didn’t open new thread, but I found some old thread.
I posted the issue there.

Thanks for your time,
Aadhavan


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