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[Levente Bicskei]

Hi! 

I'm trying to prepare a geometry for Fluent simulation and when I try to subtract solid bodies from the air volume it throws an error (not all bodies are cut out, just some). 

 

When I checked the solids to be subtract I noticed that the Spaceclaim shows duplicate facets at the solid contacts, but the "Repair/Duplicates" command is not able to delete these facets. How can I get rid of these duplicate facets without completely remodeling? (it is not possible to re-model, as I need the original complicated names, which would be a nightmare to re-write manually for nearly 100 bodies)



I've also tried using the "Pull" command to move the contacting faces away from each other, then using the "Up to" command to "touch" them again, but the same duplicate faces are displayed by Spaceclaim. It seems like if there is a problem with the tolerance of the surfaces, but when I create my own models I have never had such a problem. As far as I know the original CAD model is based on a .step file anyway.

Thank you! 

[Keyur Kanade]

You can find general procedure for fluid volume extraction in following video.
https://www.youtube.com/watch?v=Jp8btI0PCyU 

One of the main reasons in failure is geometry errors. Please check geometry in SpaceClaim. Select geometry in structure tree --> Use right click --> Select Check Geometry. The geometry should be error free to proceed. If geometry has any errors, please modify/recreate geometry at those places.

Another reason is having some tangential contacts at some circular surfaces. Please make sure that bodies are intersecting instead of just touching each other.

Sometimes bodies are in contact only at some edges. At this point volume extraction may fail. In this case as well please make sure that bodies are intersecting each other.

During volume extraction some boolean operations are done in the background. If those boolean operations fail then volume extraction fails. In this case please check if you can use "Combine" command to "Merge" all solid volumes one by one. Please check if any volume is giving any problem.

If you have only handful bodies not part of fluid volume, please check if you can use "Combine" command to subtract required bodies from fluid volume.

Please check 

SpaceClaim Demo of The Week - Extracting Volumes for CFD, MFG or Design - YouTube

Also please check share topology option. 

Please check following videos

SpaceClaim Share topology:
https://www.youtube.com/watch?v=h43E1YO1LiM

 

Please go through help manual for more details 

Regards,

Keyur

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[Levente Bicskei]

Dear Keyur,

I am familiar with fluid volume extraction techniques, but my experience is that for complex assemblies with tens or hundreds of solid bodies, the only way to get the fluid geometry is to use the subtract method. For simple pipelines or one or two complex hollow bodies they are good for internal air/fluid volume, but not for more complex cases. 

The problem is that it does not subtract solid bodies from the fluid volume for which the "check geometry" command does not show any errors. I believe this is due to the duplicate surfaces I attached a picture of in my original post. If these were fixed then the problem would be solved and Spaceclaim could subtract the body from the fluid volume. 

For some reason I can't fix these duplicate interfaces with the Repair/Duplicates command, but remodeling is not possible because each one has a special unique identifier so it would be a nightmare to remodel them one by one and manually enter their current names. (these unique identifiers needed to define the heat flux boundary conditions in Fluent)

Kind regards,
Levente

[Keyur Kanade]

Fluid volume extraction also does boolean operations in the background. You are right for geometries having many bodies, subtraction operation works many times. 

Are these duplicate faces in the same body? If it is a solid body then how it can have duplicate faces? Can you please check duplicate faces for a single body and insert image here? The image you have posted does not give any information about how many bodies are visible. Please insert more images with more explanation. 

Regards,

Keyur

How to access Ansys Online Help Document

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[Levente Bicskei]

Dear Keyur,

This is a huge assembly with 501 solid bodies. But basically the bodies have been simplified really well, so they are actually cuboids or simple bodies with straight surfaces.


If I want to subtract one from the other, I get an error, so the bodies are clearly not intersecting, and if I check just one solid body it shows no duplicate faces. 


It looks as if the tolerance of the contact surface of the two bodies is such that it perceives them as duplicates (so the 2 surfaces coincide), but at the same time you can't subtract one from the other, so they still just touch, not intersect.

Kind regards,
Levente

 

[Keyur Kanade]

From images and description it looks like you have some solid bodies and some surface bodies. 

Duplicate tool works only on visible bodies. Make sure you have only one solid body visible. Then try Duplicate. Does it show any duplicates? 

Now make only 2 surface bodies visible which are coinciding. Now use duplicate. Does it show duplicate? If yes, delete one duplicate surface body. 

You may also want to check Share Topology option. 

Also see Split Body option. 

Please go through help manual for more details 

Regards,

Keyur

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[Levente Bicskei]

I have no surface bodies, just hundreds of solid bodies. I didn't just hide them, but there is no surface body in the entire assembly.

[Keyur Kanade]

Insert an image of only one solid body. Make it transperant. How can a cuboid solid body can have surface inside it? 

[Levente Bicskei]

There is no surface inside the bodies. Two transparent solid bodies: 

Only one: 


Clearly the problem is that somehow the surface in contact is not only in contact, but also coincident. The question is how can I solve this problem without remodelling the bodies? Because at the end I'm going to need that hundreds of specific names of these solid bodies what you can see on the attached picture on my previous reply. 

[Keyur Kanade]

In the first image there are 2 solid bodies right? 

To connect these 2 solid bodies you will need to use share topology. 

Please go through help manual for more details : https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v221/en/spaceclaim/Discovery/user_manual/st_sharetopology.html?q=share%20topology

 

Please check following videos

DM Share topology:
https://www.youtube.com/watch?v=IO4ZtwZdD2I

SpaceClaim Share topology:
https://www.youtube.com/watch?v=h43E1YO1LiM

Regards,

Keyur

How to access Ansys Online Help Document

Guidelines on the Student Community

Fluids Engineering Courses | Ansys Innovation Courses