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powpow December 21, 2012 06:35

Closed geometry?
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I have a general question regarding a CAD-Model that can be used with ICEM CFD.

I have to do a simple CFD-Simulation how an additional tube in a test chamber influences the air flow.
The air enters the test chamber at Position 1. Then, one part of the air leaves the chamber through the nozzle at positon 2, the rest of the air through the new tube (Position 3).
So I build a CAD-Model of the test chamber with CATIA V5. The CAD-Model is a surface model, no solid.

I'd like to create a mesh with 10 layers of prism around the tube and the small nozzle, the rest of the volume should be filled with tetra.

Before I can do this, I have to create BODIES I think?!

Therefore I need closed surfaces I think!?

So here are my questions:

1. Do I have to add surfarces at the positions 1-3 (green circles)? Doing so would close my test chamber.

2. Do I also have to add surfaces at the positions 4-8 (red circles with green surrounding)?

3. How many BODIES do I have to create?

I couldn't find some information regarding such geometry in the tutorials or the Manual, so I would be very thankful if someone has an idea...

Cheers powpow

BrolY December 21, 2012 06:57

Close surface 1, 2 and 3.
Leave the others open in order to let the fluid flow inside your geometry.
Just create one body (fluid for example) and that should work.

I would strongly recommand to do a build topology before doing the tetra mesh.

powpow December 21, 2012 07:12

Thank you for your fast Response!

I'll try it but one question regarding the BODY:
I have to use "material Point" - "Centroid of two Points" I think!?
Which screen locations do I have to select? On surfaces or curves? And where, do they have to be? On the left and the right wall of the camber?

BrolY December 21, 2012 08:31

Centroid of 2 points is ok. You don't mind about the location, just put it in the middle of your geometry.

powpow December 21, 2012 09:17

1 Attachment(s)
Thanks a lot:)
Ok, I've closed surface 1-3 and imported the .igs into ICEM CFD.

Then I build topology, the result is shown in the Image.

Red and blue curves are okay!
Yellow curves means that the curve is shared by only one surface and of course the running-in of the two nozzles and the tube are shared by only one surface. I hope this is no Problem?!

BrolY December 21, 2012 10:34

Can you share your geometry ?

What tolerance did you specify ?
What is the smallest element size of your mesh ?

If your smallest element size is bigger than the gap between two curves, then don't mind. Otherwise, that may cause trouble.

powpow December 21, 2012 14:46

1 Attachment(s)
First I imported the .igs into ICEM CFD 13. Therefore I enabled "Use Version 5.1 Step Translator" and "Use healing".

Then I "Build topology" with Tolerance 1.
"Inherit Part", "Split surface at T-Connections" and "Delete unattached curves and points" were enabled.

I don't know the smallest element size of my mesh yet, since I'v never created a mesh so far. As is said, I just have to do a "simple" CFD-Simulation. I don't know yet which element size will be sufficient..

Of course I can share my .igs-File!

powpow January 15, 2013 06:07

1 Attachment(s)
So, I've created a Body called Fluid and did a Build Topology .

Then, I created the mesh as follows:

Register Mesh - Surface Mesh Setup - Surfaces: I selected all surfaces, entered my values and applied.

Register Mesh - Compute Mesh - Volume Mesh - Compute.

Then, I wanted to add 10 layers of prism:

Register Mesh - Compute Mesh - Prism Mesh.
There I selected the parts for the prism layers and clicked "ok".

Then I clicked surface mesh up, chose the surfaces of the tube and the small nozzle and applied.

Then: Register Mesh - Compute Mesh - Volume Mesh. I enabled create prism layers and computed.

I exported the result with the Register Output - Select Solver. I chose Ansys CFX and ANSYS and applied.
Then Register Output - Write Input and enabled BINARY instead of ASCII.

Then I started CFX-Pre - New case - Simulation Type: General
Click with the right mouse button on mesh - import mesh - ICEM CFD and chose the created .cfx5-file.
As you can see in the image lost inner geometry I "lost" the whole inner geometry!

I hope someone finds my mistake?:)

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