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N.R. June 6, 2007 12:01

Interpolating volume data onto quad surface mesh
 
Hello

I am looking for a way to interpolate the results stored in a volume mesh (tetrahedrals, created with ICEM, solved with CFX) to another surface mesh (quad surface mesh). The surface is one of the boundaries of the volume region.

I know there is an interpolation function in CFX but it looks like it would only accept volume mesh to volume mesh interpolation. I can see the way to solve this problem with a subroutine and some programming but I there is a feature in CFX or some body has encountered the same problem please let me know.

Which format do you suggest for importing a quad surface mesh into ICEM or CFX? It would need to be an open (ASCII) format since the vertix data is produced by a FORTRAN code. I tried Plot3D but have troubles importing it. Can someone send me a simple ASCII plot3d file that worked with ICEM?

Thanks in advance N.

Joe June 6, 2007 12:33

Re: Interpolating volume data onto quad surface me
 
The first part of you problem is easy to solve. Just use the export function in CFX post to export the data for the surface meshes you are interested in.

Icemcfd imports a large number of formats ... you should be able to get your raw mesh data into one of them.


N.R. June 6, 2007 14:45

Re: Interpolating volume data onto quad surface me
 
Maybe I was not precise enough, when posing my question:

The surface mesh I want to interpolate on is not identical to the boundary mesh of my volume mesh. It is just that the mesh I want to interpolate on covers the same (geometrical) surface.

Example: Think of a tube after volume meshing with ICEM-> tetrahedral volume mesh and a triangular boundary surface mesh. There is another surface mesh made out of quadrilaterals that also forms a tube of the same diameter & lenghth. This comes from another program, not CFX/ICEM. Now I want to interpolate the solution of the volume mesh from CFX(e.g. shear stress on the wall) onto the quad mesh.


Joe June 6, 2007 14:50

Re: Interpolating volume data onto quad surface me
 
No problem.

Export the results you want to use as BCs under CFX Post.

Create the new mesh and import it into CFX Pre. Import the exported Post results and impose them as a BC.

Very simple once you've done it once. Look at the tuts ... one of them does exactly this.

brunoc June 6, 2007 14:55

Re: Interpolating volume data onto quad surface me
 
Joe was right. It doesn't matter that your mesh is different. CFX-Post has a tool that exports data on surface parts ('File > Export: Type = BC Profile'). You can then import it into CFX-Pre ('Tools > Initialize Profile Data'). The solver will interpolate the data you exported into your new mesh boundaries.

N.R. June 7, 2007 08:14

Re: Interpolating volume data onto quad surface me
 
Thank you for the tips. But what if I do not want to use the interpolated results as a BC? I only need them as output, but there is no export feature in CFX pre.

Also, can you import just a surface mesh into CFX pre. ICEM won't write an output file without volume elements. Volume meshing the surface mesh that I want to interpolate on doesn't work, since it has akward surface elements that I want to interpolate on.

To clarify the question and summarize previous results: Is there a way to import an external surface mesh in any CFX product. Then interpolate the results at the wall (e.g. wall pressure) of a CFX result file onto the surface mesh. Then output the results of that interpolation. (e.g. format 'x y z variables') The results will not be imposed as BCs in CFX but used after export in another program.

I was thinking of using cfx5interp for obtaining values at the nodes of my external surface mesh, but this will give troubles since the external surface mesh is located at the wall of my volume mesh. This will produce a lot of external points with values '0.0E0' instead of interpolating using the nearest wall point.

Hope this makes it clearer. Thanks for the help so far.


N.R. June 7, 2007 08:15

Re: Interpolating volume data onto quad surface me
 
Thank you for the tips. But what if I do not want to use the interpolated results as a BC? I only need them as output, but there is no export feature in CFX pre.

Also, can you import just a surface mesh into CFX pre. ICEM won't write an output file without volume elements. Volume meshing the surface mesh that I want to interpolate on doesn't work, since it has akward surface elements that I want to interpolate on.

To clarify the question and summarize previous results: Is there a way to import an external surface mesh in any CFX product. Then interpolate the results at the wall (e.g. wall pressure) of a CFX result file onto the surface mesh. Then output the results of that interpolation. (e.g. format 'x y z variables') The results will not be imposed as BCs in CFX but used after export in another program.

I was thinking of using cfx5interp for obtaining values at the nodes of my external surface mesh, but this will give troubles since the external surface mesh is located at the wall of my volume mesh. This will produce a lot of external points with values '0.0E0' instead of interpolating using the nearest wall point.

Hope this makes it clearer. Thanks for the help so far.


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