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Member
mr_siegel
Posts: 3
Registered: ‎02-02-2013
Accepted Solution

Creating external volume around 3D mesh model

890 Views, 14 Replies
02-13-2013 12:50 PM

We’re working with a customized developing software which can export our 3D models as NASTRAN.dat file format (inherently a 3d format). During the imported with Autodesk Simulation CFD (ASC) the following message pops up:

 

The 2D model is either not planar, or it is not in the Z = 0 plane

1.JPG                       

 

Seems that ASC interpret the file as 2D model even if I have later a 3D model in ASC:

2.jpg 

 

The problem that occours now: I can’t set up an external volume. Both possibilities to access External Volume Creation don’t work:

 

Setup (tab) > Setup Tasks (panel) > Geometry Tools, and click the Ext. Volume tab.

Alternatively, right click on the Geometry branch of the Design Study bar, and click Edit...

 

I exported also a few 3D models with merged surfaces as *.obj file and imported them into Inventor Fusion 2013. The import wors without any error message but afterwards I’ve the same problem: I can’t create the external volume:

3.jpg

 

 

I checked the tutorials and it works fine with the car models etc. but not with our 3D model. Any suggestions?

 

Thx

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Royce_adsk
Posts: 645
Registered: ‎08-24-2011

Re: Creating external volume around 3D mesh model

02-14-2013 06:57 AM in reply to: mr_siegel

Could you upload your 3D model for us to checkout?

 

Thanks,

Royce



Royce Abel
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Member
mr_siegel
Posts: 3
Registered: ‎02-02-2013

Re: Creating external volume around 3D mesh model

02-14-2013 10:38 AM in reply to: mr_siegel

Following the models (see attachment):

 

TestWing_1.dat (NASTRAN File)

TestWing_2.obj (WaveFront OBJ File)

 

 

Beside this I can export the 3D model as:

 

4.JPG

 

Please let me know if you need some other files.

 

Thanks for your help!

 

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Product Support
Royce_adsk
Posts: 645
Registered: ‎08-24-2011

Re: Creating external volume around 3D mesh model

02-14-2013 12:05 PM in reply to: mr_siegel

Interesting list. Try saving it as a Solidworks file and upload that.  Haven't had a chance to look at the other 2 files you posted, but maybe someone else will get to it before I do.

 

-Royce



Royce Abel
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Member
mr_siegel
Posts: 3
Registered: ‎02-02-2013

Re: Creating external volume around 3D mesh model

02-14-2013 12:53 PM in reply to: mr_siegel

"Good" choice - solid works is the only file format which I can't create. For the export solid works must be installed on the computer but I'm an AutoCAD 'aficionado' :-) So no solid works on my computer...

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Product Support
Royce_adsk
Posts: 645
Registered: ‎08-24-2011

Re: Creating external volume around 3D mesh model

02-14-2013 01:38 PM in reply to: mr_siegel

Well, that is a bummer!  Too bad it didn't output a better Autodesk format.

 

-Royce



Royce Abel
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Active Member
surfdabbler
Posts: 10
Registered: ‎02-07-2008

Re: Creating external volume around 3D mesh model

02-15-2013 03:58 AM in reply to: Royce_adsk

Hi, I'm the developer of the software making the original export model.  I can get the model into Solidworks format, although the files are often around 50Mb in size and take a long time to generate through Solidworks, and this format is not supported by Autodesk Simulation CFD.

 

We would really like to work with the NASTRAN format files, as these are generated quickly and easily, and are supported by Autodesk Simulation CFD.  Please let me know what is going wrong with the import of those files so that we can get these working.  The file is definitely a 3d format, and we can see the 3d model in the CFD program, but for some reason it will not allow analysis of this as a 3d model for external flow, as mr_siegel has described.

 

 

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Product Support
Royce_adsk
Posts: 645
Registered: ‎08-24-2011

Re: Creating external volume around 3D mesh model

02-15-2013 05:54 AM in reply to: surfdabbler

1) We can read Solidworks files using Inventor Fusion which is included in the CFD installer.  Once it is in the SolidWorks format, we might be able to read it into Fusion and convert to a 3D geometry.  Depends on the quality of the geometry.

 

2) The Nastran import needs to be a 3D mesh and what you actually have is a grid mapping of surfaces (CQUAD4 Element). That is why you see so many errors when you load the model.  The nastran import does not support the geometry tools because the assumption is that you have already meshed your model for simulation.  If you wanted to use only the CQUAD4 elements it would have to be located on the XY plane for a 2D analysis.

 

You are seeing the surfaces in CFD, but that is after you went through many error messages indicating that something was not correct.  The model will not work as is.

 

3) The .obj and Nastran fails to open in both Inventor Fusion and Inventor Pro.



Royce Abel
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Active Member
surfdabbler
Posts: 10
Registered: ‎02-07-2008

Re: Creating external volume around 3D mesh model

02-16-2013 06:39 PM in reply to: Royce_adsk

Yes, I have used the CQUAD4 elements to define the surfaces in the NASTRAN file.  The NASTRAN format does not support a "MESH" as such.  Do I need to use CHEXA, CPENTA and/or CTETRA to define my model as a solid?  I could convert each CQUAD into a CHEXA with a small thickness if this would help.

 

Does Simulation CFD support analysis of surface-based models and membranes?  Our models are constructed from cloth, and for some models (not so much this particular one), it is important to analyse the flow on both sides of a single layer of cloth, so a membrane based model would be perfect.  However, I know that many CFD packages cannot analyse surface models, and require the model to be given a solid thickness before analysis can be done.  Is this the case for Simulation CFD?  If so, is there a minimum thickness required?  (e.g. Some PARSOL analysis software requires at least 1-2mm thick surfaces, otherwise flow may occur through the surface.) 

 

Do you have a sample NASTRAN file that does work in Simulation CFD?  Even a simple geometry would be helpful as a reference, so that I can mimic the model definition method used in that file - even just a cube.

 

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Active Member
surfdabbler
Posts: 10
Registered: ‎02-07-2008

Re: Creating external volume around 3D mesh model

02-20-2013 04:06 PM in reply to: surfdabbler

I have made a solidworks model to test with.  Getting this file working will not solve the main problem of interfacing between programs, as mr_siegel does not have Solidworks to use, but will be an interesting model for mr_siegel to test with.

 

www.surfplan.com.au/temp/Part1.zip

 

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