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-   -   [ICEM] Meshing strategy/values (http://www.cfd-online.com/Forums/ansys-meshing/111847-meshing-strategy-values.html)

powpow January 16, 2013 12:55

Meshing strategy/values
 
2 Attachment(s)
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:confused:

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..

diamondx January 16, 2013 12:57

It is better to post this problem in the CFX section you get lot of helps there

powpow January 16, 2013 13:40

Thank you for your advice, I will try it there:)

Far January 16, 2013 16:41

Quote:

Originally Posted by powpow (Post 402267)
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:confused:

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..

Mesh is one of the possible problem.

powpow January 16, 2013 16:58

Thanks! Do you know how I could create a better mesh:)

Far January 16, 2013 17:00

Through ICEM Hexa.

powpow January 16, 2013 17:13

And which Parameters should I try?

BrolY January 17, 2013 04:37

Tetra+Prism can create good meshes too which can give good results ...
Hexa meshes can provide, sometimes, better results, but if your computation parameters are wrong, it would give you the same bad results as with tetra+prism meshes.

So I think, you should first ask your question to the CFX forum, and if all your computation paramters are good, come back here with pictures which show the problem on the mesh ..

powpow January 17, 2013 14:15

1 Attachment(s)
Thank you for all of your advice:)

I created my first mesh which could be solved!
My procedure was the same as described in the ICEM CFD Tutorial "Tetra/Prism Mesh Generation for a Helicopter" except the following changes:

- To generate the Octree Mesh I entered 0 (=autosizing) for "Max element" at the Global Element Seed Size in the Global Mesh Size Setup.

- My Part Mesh Setup is shown in the picture below.

- I created no density box!

Do you have any hints what can be done better?

E.g. what can I do if I want a finer mesh?

Far January 17, 2013 14:34

try patch dependent mesh....

powpow January 17, 2013 16:28

at which step?

Far January 17, 2013 16:53

on surfaces and fill volume with denauly. Your other setting e.g. int wall seems correct.

powpow January 18, 2013 04:41

When looking at CFD-Post at the moment, I found another problem :

I built my CAD-Modell in Catia in mm. The scale at CFD-Post now says it's in m?!

What do I have to change?

Far January 18, 2013 12:39

scale in either ICEM or CFX-Pre/Fluent....

But if the length dimension are still the same, I mean if you have generated 1000 mm length and CFD-post is showing 1 m instead then no need to worry.... That can also be fixed in CFD-post...


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