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 pranab_jha March 18, 2010 16:19

Meshing a cylindrical volume

Hi
I want to mesh a 3d pipe. How can I do that?

What I tried was: I meshed one face (275 cells) and tried to sweep that face along the axis of the pipe to form the volume. But the mesh density is v high. Gambit takes a default value of 1 in the axial direction. How can I control the axial density of the mesh?

Geometry:
Dia: 50 mm
Length: 12.7 m
Approx nodes reqd: 38000.

 pranab_jha March 19, 2010 00:03

Or.. I should put the question like this...
How can I mesh a 3d pipe in Gambit using hex elements?

 -mAx- March 19, 2010 01:55

Build first the geometry.
Then deal with the mesh.
Once your pipe is build, mesh one cap with quad-pave, and then mesh the volume with the desired element size.

 pranab_jha March 19, 2010 02:56

I did mesh one cap with quad-pave. What option do I choose to control the element size. Is 'cooper' the best option and do I specify the interval count/size appropriately in the axial direction?

 -mAx- March 19, 2010 03:54

Yes Cooper is the best option (if your volume enables it).
If the cap is meshed, (and you are using Cooper), then the surface mesh for caps are fixed. The "mesh-freedom's degree" remaining is the axial one, so giving the element size for the volume mesh, will be the element size for the axial direction.

Else you can mesh one edge in axial direction, and it will govern the volume mesh densiy (you can try to give a very fine element size for the volume mesh, but as the axial edge is already meshed, this volume element size will be ignored, since you don't enable the delete lowe mesh option)

 pranab_jha March 20, 2010 11:00

Thanks Max... that was really helpful

 pranab_jha March 22, 2010 18:13

Hi,

I have another problem now. I want to split the inlet of my mesh into two equal parts-upper and lower for two different fluid inlets. How can I do that?

I created a semi-circular face first and then swept it to make myself a "semi-cylinder". Then I mirrored it to get myself two semi-cylindrical geometries with mesh. But the problem is that the two new faces generated due to this (interface between the two semi-cylinders) is taken as a wall when I export the mesh to fluent. I only want two inlets and one outlet to allow mixing of the fluids.

Thanks,
Pranab

 -mAx- March 23, 2010 01:46

your "interfaces" seem to be not connected.
You can connect them in gambit (Surface/Connect)

 Sidewinder March 23, 2010 06:07

Similar Problem

post removed!

 pranab_jha March 23, 2010 15:58

I did get my geometry and mesh right (finally). But I used very basic method to do that.
-I created two semi-circular faces (like a circle) at both ends of the pipe.
-I made faces out of the pair of upper and lower circles.
-I joined the two faces to make the pipe volume. Then I specified the inlet conditions for the two fluids at the two inlet faces.
But I would like to know how I can mirror a half cylinder to form two cylinders (described in my earlier post) and neglect the interface as I do not need it. I will give Max's suggestion a try and see.

 -mAx- March 24, 2010 01:55

you can copy your volume, enables reflect option and give the right direction's vector. Also enable copy mesh unlinked option. Depending on your coordinate system, you may have to aligne your reflected volume for "glueing" it with the original one.
Then connect the interfaces each other.
Watch out sometimes, the connect operation delete the volume mesh, and you will have to remesh it

 Sidewinder March 24, 2010 06:56

post removed!

 -mAx- March 24, 2010 07:10

post a picture, or mail me your geometry

 Sidewinder March 24, 2010 09:17

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post removed!

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