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 ANJUM NAVEED February 20, 2006 14:50

question

hi i have three questions 1) is it possible to describe wall thickness in gambit. or we have to give it in fluent. i saw in tutorial u can describe wall thickness in heat transfer model but what if there is no heat transfer but wall thickness is important.

2) if i prepare a geometry with two volumes like two cylinder second one start right from there where first one end. and mesh them separately now when i will import this mesh in fluent will fluent will take it continous mesh. if not how can i make them continous.

3) in 3-D prob if i mesh only all side of vloume will it be enough or i have to mesh whole volume.

Anju

 Jason February 20, 2006 16:23

Re: question

1) What else are you going to use the wall thickness for? If the wall affects the flow (like the flow sees the end of the wall which has a thickness instead of just an infinitely thin plane) then you should physically model it in Gambit. If you're not using it for heat transfer, and the flow doesn't see the "thickness" dimension of the wall, then why else would you want the wall thickness?

2) Fluent will not see it as a continous mesh just because the mesh is next to one another. You can either "connect" (in the face commands, it looks like a black plug) the ends of the cylinders so that they share a common face and then mesh the volumes. Since both volumes share this face, the mesh on the face will be common to both volumes and when you export the mesh Gambit recognizes this as being a continuous mesh and nothing else needs to be done. If you want to have a non-conformal mesh at the intersection (say one volume uses tet meshes and the other uses hex) then you have to define each of these faces as an "interface" when defining your BCs. Then when you load the mesh into Fluent you have to go to Define->Interfaces and tell fluent that those two "interface" BCs should be one single non-conformal interface. Either way works. I recommend connecting the face because in a poor mesh, a non-conformal interface will further add to the error in your solution.

3) You MUST mesh the volume. Without internal elements, Fluent doesn't have anywhere to interpolate, calculate, or save the flow field data. If you can't mesh within Gambit (sometimes complicated geometry will cause Gambit to fail) then you can try TGrid.

Hope this helps, and good luck, Jason

 ANJUM NAVEED February 20, 2006 19:48

Re: question

hi thanks it was very informatic. for pipe thickness look it like there are two pipes havng different dia meter and one pipe has gone deep in other pipe and flow is in direction of pipe.now here the pipe who is in side its thickness effect the flow. how can i produce thickness for second pipe. thanks Anjum

 Jason February 21, 2006 09:19

Re: question

1) Create a cylinder that is the right inner diameter and length of the large pipe (Cyl-A) which is the flow domain for the larger pipe. 2) Create a cylinder that is the right outer diameter and length of the small pipe and move it to the right location (Cyl-B). 3) Create a cylinder that is the inner diameter and length of the small pipe and move it to the right location (Cyl-C). 4) Subtract Cyl-C from Cyl-B (results in Cyl-D) which is the physical geometry of the smaller pipe. 5) Subtract Cyl-D from Cyl-A which results in the flow domain you were looking for.

Hope this helps, and good luck, Jason

 ANJUM NAVEED February 21, 2006 16:12

Re: question

thanks

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