CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   CFX (https://www.cfd-online.com/Forums/cfx/)

 CFX 4.3 user February 20, 2002 10:12

Hey people,

I am building a relatively simple setup using CFX 4.3. A room with rectangular inlet and outlet, with five small heat generating rectangular prisms sit on the floor of the room. The application of constraint really annoys me. I have applied advanced constraints on the floor of the room and base of all the five heat generators, I can mesh it but while I run volmsh, it comes that inconsistentelements formed. I could not find any clue on the manual, Is there any one who knows the problem?

CFX4.3 user

 CFXboy February 20, 2002 11:14

The problem you are facing is that some of the nodes and the mesh seeds are not located at the same position, resulting in triangular meshes and inconsistent elements. Inconsistent elements mean that the number of elements on opposite faces are not equal. To solve the problem, I would recommend you using the simple constraints, which is much easier.

If you have no choice but to use advance constraint, make sure the nodes and mesh seeds are located on the same spots. This can be done by associate/curve/curve command. I believe you might have done this. Sometimes, this might still result in inconsistent mesh. The next step would be to create the subordinate surface (surfaces that cover the floor) so that the endpoints of the subordinate surface are located at the mesh seed. For example, if you would like the floor to have mesh seeds of 6 by 6 and a 2 by 2 inlet patch in the middle, first create 9 surfaces of 2 by 2. You can create another 2 points on the floor edges using the create/point/interpolate command. Make sure the manifold command is on if your floor is not flat. With this command you can create several more points on the other floor edges. Next create the curves between the points that you have just created (manifold if surface is not flat) and create the surbordinate surfaces by create/surface/manifold command. Finally, associate the curves after you create all the subordinate surfaces.

I hope this helps.

CFXboy

 CFX 4.3 user February 20, 2002 11:27

CFX Boy

As the manual recomends I create subordinate surfaces the completely covers the whole floor by Geometry/create/surface/vertex command,. Then I associate the overlaping curves of the big room and the smaller subordinate using Associate curve curve. Then I meshed the whole geometry using 0.1 element length. That was how did it, this thing really making me crazy for about a month, I will try it again using your suggestions.

CFX 4.3 user

 cfd guy February 20, 2002 12:46

Hi,
Instead of wasting a lot of your time trying to know how the advanced constraint works, why don't you break your single block into N blocks so that you have a specific surface (patch) for every of your five heat generators giving you no meshing problems? I only have used single constraint and with great care, but advanced constraints I gave up how it works a long time ago.
Good luck! cfd guy

 CFX 4.3 user February 21, 2002 04:41

Hi cfd guy,

Thank you very much for your reply. I do not understand you when you say 'break the block' I have five solids sited on the floor. All the five are different solids, I am creating a constraint between the lower face of each heat generating blocks and the floor of the room, that was the idea which wanted to be implemented.

Have a blessed day

CFX user

 cfd guy February 21, 2002 10:05

Hello again,
I guess I know what is your problem. Actually you have 6 solids, 5 heat generators and 1 big room. The main thing is that you cannot generate your mesh just creating several blocks inside and one bigger outside. You must satisfy some conditions and this conditions are the Multi-Block structure used by CFX-4. If you are begginer in the code, I'd suggest you to take a look at CFX-4 manual or even visit the CFX Comunnity Pages and download some online courses that might help you in your journey.

Regards, cfd guy.

 cfx 4.3 user February 22, 2002 09:50

Hi cfx Guy

You propose to break the heat generating blocks into N blocks in order to avoid implementing advanced constraints, and having no problem during meshing. Can you explain me how to do it? I really do not know this method.

Best regards

cfx 4.3 user

 cfd guy February 22, 2002 11:16