Geometry not visible

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

I imported my nastran file in VWT but it doesn't show the geometry in VWT even after showing 'imported file successfully' What should I do?

 

 

<?xml version="1.0" encoding="UTF-8"?>Screenshot (8).png

Tagged:

Answers

  • ydigit
    ydigit
    Altair Employee
    edited February 2016

    How did you export .Nas file? Make sure to use CFD Profile and Nastran(Fluent) file format.

    Is the scaling correct?  Make sure the model is scaled to 'meters' before export from HM.

     

    Press 'F' to get full overview of the current model. If none of the above works, please upload the model.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited November 2020

    Geometry is 2.5m long. Here's the hm file. Nastran's too big to upload. Everything was fine whatever you said above. When I ran the simulations, it showed nothing is there in the tunnel. Is there a generate kind of feature in VWT? Meanwhile here's the hm file , do export it in nas and check yourself. nas file is too big to upload

    Unable to find an attachment - read this blog

  • ydigit
    ydigit
    Altair Employee
    edited February 2016

    I am able to import the model in the VWT13.1

    It needs to be scaled down by factor 1000! HM should show 2.5 'unit' as distance between two ends.

     

    The mesh 4+ Million surface elements! Thats too much unless you have access to HPC resource. In order to generate volume mesh for such a fine surface mesh, you would need a big machine. Probably 128 GB RAM and dozens of cores!

    I guess that is what is happening in your case. Could you send a screenshot of VWT run folder? Does it contain CAD.DIR, MESHSIM.DIR, etc? Post the *MeshSim.txt in case it generated.

     

    Best bet, coarsen the mesh to ~ 200k elements and try running.

     

  • ydigit
    ydigit
    Altair Employee
    edited February 2016

    Mesh similar to the one in this student car should work on a non-HPC machine. Mesh your model similarly. In order to run faster, use tria mesh. http://www.altairuniversity.com/analysis/cfd/virtual-wind-tunnel/virtual-wind-tunnel-analysis-of-a-student-race-car/

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited February 2016

    But then won't it make a difference in the real and VWT simulations because if we use a smaller scale model, then we need to change pressures and temperature inside an actual wind tunnel to make the simulations identical to real life.

     

    I can let the simulations run for 4-6 hours. I'm using the coarse mesh. So would that be okay with the current dimensions? Okay, I'll use tria and I'm too using VWT 13.1. Could you send me the nas file?

    <?xml version="1.0" encoding="UTF-8"?>Screenshot (9).png

  • ydigit
    ydigit
    Altair Employee
    edited February 2016

    I should have been more specific about 'scaling' issue.

    HyperMesh is unitless. However it is easier to work in HM, if one works in quasi 'mm' unit. E.g in your case 2500 'mm'/'unit' the car length.

    VWT assumes the car to be in 'meters'. Hence one has to scale by factor 1000 before exporting .Nas from HM.

    So in your case you scale mm>m in HM and export that .Nas file.

     

    Your .stmod file with ~480MB is probably containing a very fine (surface) mesh. It is unlikely to work with a standard laptop/PC.

     

    I am not sure which .Nas file are you asking for. The student car model can be downloaded from the above link or

    http://www.altairuniversity.com/wp-content/uploads/2014/05/rcmain.zip

    This model should run in few hours.

     

     

     

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited February 2016

    Great! Understood! Thank you very much! :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20'>

Categories