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Old   January 16, 2013, 13:38
Default Meshing strategy/values
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Hello,
I'm a newbie with meshing. But with the help of some tutorials and this forum, I was able to create my first mesh.

Since it is my first mesh, I don't know at all which values should be entered

To get an impression of the size, the dimensions of the test chamber are:
Length: 14 458 mm
Diameter: 3032 mm

So I tried it this way:
- Register Mesh - Surface Mesh Setup - Surfaces: I selected all surfaces, entered Maximum size: 150, Height: 150, Min size limit: 20 and all others: 0 - Apply.
- Register Mesh - Compute Mesh - Volume Mesh - Compute. Volume Mesh is Tetra/Mixed and Mesh Method is Robust (Octree)
- Check Mesh and ignoring multiple edges and single edges since they shouldn't be a problem. Delete unconnected vertices.
- Then, I wanted to add 10 layers of prism:
- Register Mesh - Compute Mesh - Prism Mesh.
- There I selected the parts for the prism layers, entered there num layers =10 and clicked "ok".
- Then I clicked surface mesh up, chose the surfaces of the tube and the small nozzle, changed Maximum size: 50, Height: 5, Min size limit: 10, Height Ratio: 1.5 and applied.
- Register Mesh - Compute Mesh - Volume Mesh. I enabled create prism layers and computed.
- Check Mesh and again ignoring multiple edges and single edges.

The result is shown in image001.

Unfortunately, some errors occured while doing the simulation with CFX-Solver Manager (see image002).

I hope someone can tell me, if the problem was the mesh or perhaps adjustments in CFX-Pre..

As I said above, I did never meshing before, so if someone can tell me better values than mine I would be very happy
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File Type: jpg image002.jpg (68.3 KB, 9 views)
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Old   January 16, 2013, 17:41
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Your simulation runs for a bit then fails, so refer to these FAQS:
http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F
http://www.cfd-online.com/Wiki/Ansys...gence_criteria
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Old   January 17, 2013, 00:52
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Octree volume meshes are not generally good for CFD. Use octree to get a good surface mesh then delete the volume elements and remesh the volume using Delaunay. Also you must smooth the mesh. It sounds like you are using ICEM CFD. Smooth until the "quality" is at least 0.3. You can also look at the meshing forum if you need help with meshing.

It's not possible to tell if your mesh size is good or bad. You need to run a mesh sensitivity study to determine if the mesh is fine enough or not.
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