Problem with my Autodesk CFD model

[mariowp4ever10]

Hello, i am using Autodesk CFD to perform a wind tunnel test for my diploma thesis. My model is a mountin system for solar panels. When the analysis completes, there are some members flowing around as you can see in the 3rd screenshot. Does anyone know what is the problem? I am using Autosize for meshing. I have already used edge merging tool. The model was built in fusion 360. Please help!

In the screenshots you can see the model diagnostics and the members flowing.

  

 

[marwan_azzam]

Hello @mariowp4ever10 ,

Not sure what you mean by "there are some members flowing around"

Can you post the model? (Zip the cfz file).

Marwan

[mariowp4ever10]

Hello!

Thank you for your response! I am attaching the zipped cfz file and one screenshot. The problem occurs when i choose to add a plane. I am sending you only the support file (without mesh and results) beacause the one with the results is huge. For meshing i just used the autosize and for wind velocity i entered 25m/s.

Thank you very much!

Marios

 

[marwan_azzam]

Hello @mariowp4ever10 .

Thank you for posting the model. Before I go ahead and look at it, what actually is the problem.

I'm still not clear on what the problem is. Can you elaborate?

Marwan

[mariowp4ever10]

Hello,

In the screenshot i sent you in the last message, you can see some members of the structure that have been separated from the structure. I dont know why this happens and what impact it has at the analysis results. I am resending the screenshot. I think it is clear that there is a problem. I just want to know what is wrong, beacuse i am new to autodesk CFD and i wanted someone to explain me. I believe it might be a meshing problem or a problem with the model, but i am not sure.

Marios

 

[marwan_azzam]

@mariowp4ever10 

Can you post the model? (Zip the cfz file).

Marwan

[mariowp4ever10]

I already posted it before. I am posting it again. 

[marwan_azzam]

@mariowp4ever10 

I know you posted a zip file. It's a zip of the wrong file.

In order to have the CFD model, I need the support share file (*.cfz) and not the cfdst file. The cfdst file is like a table of contents and does not have the geometry or any FEA data in it.

You sent me the cfdst file as shown in image below.

So again, can you post the model? (Zip the cfz file).

[mariowp4ever10]

I am sorry my friend. I hope the file i am sending now is the crrect one. Thank you for your understanding. 

Marios

[marwan_azzam]

@mariowp4ever10 ,

Thank you for posting the model. I was able to open the model and run the analysis.

You state the problem as being:

"Some members flowing around"
"The problem occurs when i choose to add a plane"
"Some members of the structure that have been separated from the structure"

Are you referring to the red Xs pointed by the black arrows in image below?

If so, these are just graphical glitches that appear in the Planes view.

If you switch back to the Global view they go away as see below:

Please let me know if I got this right.

Marwan

[mariowp4ever10]

Hello, 

Thank you for your reply! 

Yes when I switch to global everything is ok

So they are just glitches and not some problems with meshing or model?

I also would like to ask the following:

1) In the meshing diagnostics there are many arrows showing edges and surfaces problems. What can I do with them to run a correct analysis?

2) Is autosize accurate for this model or I should use manual meshing?

3) What is the effect of surface refinement ? Should I use it in my model?

Thank you very much again!

Marios

[mariowp4ever10]

Can you tell me please? It is very important for my diploma.

Thank you!

[marwan_azzam]

@mariowp4ever10 ,

Sorry for the delayed response.

Yes, those are just graphical glitches and you can ignore them.

1- You can use the geometry tools and merge edges. If the model meshes with no issue, which it does, I would not worry about it.

2- Autosize does not always generate a very good mesh. It depends on the geometry and how much detail there is. In your case it's not too bad. But with any FEA analysis mesh size if very important so you might want to run with a finer mesh to see if that has much effect on your results.

3- You can learn more about surface refinement here.

Marwan

[mariowp4ever10]

Hello my friend, 

How can i make a finer mesh ? 

Thank you,

Marios

[marwan_azzam]

@mariowp4ever10 ,

The documentation is a good resource on how to control the mesh size.

See this section:

https://help.autodesk.com/view/SCDSE/2023/ENU/?guid=GUID-AA5E9A73-6088-476A-88E5-CADE9951A1A2

Marwan

[mariowp4ever10]

Okay! Thank you for your help. 

Also when i insert wind velocity to perform a wind tunell test, the static pressure in results refers to wind pressure ?

[mariowp4ever10]

?

[marwan_azzam]

Yes, the pressure is that of the fluid.

Marwan