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-   -   doubt on meshing a cylinder (http://www.cfd-online.com/Forums/fluent/37349-doubt-meshing-cylinder.html)

FELIX JOE S July 22, 2005 12:55

doubt on meshing a cylinder
 
Sir,

I am a student learning fluent in IIT Chennai. I had a problem in meshing a cylinder of 0.004m(outer diameter) and 0.0037m(inner diameter) [i.e. thickness of 0.0003m ] and a height of 0.02m height. So the problem is that the meshing error(in the Gambit) is occuring .I used all the three basic volume meshes. The error is that " SIGSEGV (segmentation violaton) error" . All occurs for the mesh size of 0.0001 . please suggest me ways to solve it.

thanking you

JOE

MANIVANNAN July 22, 2005 13:06

EXPLAIN ME ABOUT AN ERROR
 
Sir,

I am a student learning fluent in IIT Chennai. I had a problem in axis symmetric valve the problem is in fluent which says divergence detected in AMG solver: X momentum the inlet we give as total gauge pressure & outlet is pressure which is 0.

please suggest me ways to solve it.

thanking you

AJG July 22, 2005 13:31

Re: EXPLAIN ME ABOUT AN ERROR
 
I think u are using to many nodes! the density is to high for your server. Try a more coarse mesh.

Mahesh July 23, 2005 00:31

Re: doubt on meshing a cylinder
 
create a cylindet of 4 & 3.7 as dimensions. in Fluent, say grid is created in mm. So it will take new dimensions as 0.004 & 0.0037

Mehdi Ghoddosy July 23, 2005 02:21

Re: doubt on meshing a cylinder
 
Dear Felix:

What meshing scheme are you using? I think using Map scheme can help you. However if you decet you meshing scheme i can give you more offers.

Best Regards

Swarup July 23, 2005 05:15

Re: EXPLAIN ME ABOUT AN ERROR
 
Check your problem set-up, especially your boundary condition values. I hope you understand what is meant by divergence. your variable values are going out of bounds. Are you getting some messages before divergence detection message is thrown? Swarup.

sharuk July 23, 2005 11:47

Re: doubt on meshing a cylinder
 
use size function

FELIX JOE S July 25, 2005 07:36

Re:Re: doubt on meshing a cylinder
 
Sir

I have tried it doing that also but the error is in the mesh of that length to thickness ratio (as i think). The mesh scheme i used predominently was TET/HYBRID still i also used Hex Map. I also modeled it in mm still the same error is present.I still need the mesh size for both i.e. (1) if i model it in same size (2) if in scaled one but i have tried both of it. I still need more advice

Thank you for your valued suggestions

JOE


FELIX JOE S July 25, 2005 07:45

Re:Re: doubt on meshing a cylinder
 
Sir

I have tried it doing that also but the error is in the mesh of that length to thickness ratio (as i think). The mesh scheme i used predominently was TET/HYBRID still i also used Hex Map. I also modeled it in mm still the same error is present.I still need the mesh size for both i.e. (1) if i model it in same size (2) if in scaled one but i have tried both of it. I still need more advice

Thank you for your valued suggestions

JOE


Mehdi Ghoddosy July 25, 2005 08:04

Re: doubt on meshing a cylinder
 
Dear Felix:

I think your mesh and model sizes does not have any problem, and range in conventional geometries. Also, meshing cylenders is a conventional and frequently used case in CFD problems. So, the problem arises in creating geometry or meshing process. To avoid this, first forget your cylinder thickness and try to mesh remaining geometry. Fisrt, grade start and end caps(circles). Split them to four curves and try to mesh the cap surface using Map scheme. Then, grade the cylinder wall, and mesh it using Map scheme. Now, mesh the volume using Map or Cooper scheme. Following this concept no problem should be arised. If you got the error again, there is an error in your program, or concept of defining mesh or geometry. If no problem arised we would discuss about ramainnig part of your model. Good luck.

Best Regards

Mehdi Ghoddosy


Mehdi Ghoddosy July 25, 2005 08:08

Re: doubt on meshing a cylinder
 
Dear Felix:

Excuse me, forgot to say, create the geometry using down-top approach. Means that first create the circles and then wall surface, then compose the volume using these faces.

sharuk July 26, 2005 03:44

Re: EXPLAIN ME ABOUT AN ERROR
 
this is for manivannan, check ur boundary conditions, and reduce the relaxation factors.if it doesn't work go for coupled/implicit solver.i'm in krishna hostel, room no 111, no. 9884204548, tell me if u got it correct. sharuk

zxaar July 27, 2005 04:06

Re:Re: doubt on meshing a cylinder
 
why don't you try making mesh in mm and then scale it in fluent. if the problem coming from mesh dimensions. otherwise sigmentation violation suggest that there is a problem with your geomtery. check that.

Mehdi Ghoddosy July 27, 2005 08:06

Re:Re: doubt on meshing a cylinder
 
Dear Felix:

Excuse me, if I have not read your message carefully; but as I remember you said that tried to generate the mesh with dimension in mm and got the error again. However, if you have not tried to generate your mesh in mm, I recommend try it first.

Regards Mehdi Ghoddosy


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