General Mechanical

General Mechanical

Why does my mesh fail ?

    • aslzynperl
      Subscriber

      Hello,

      I'm cyurrently working on an acoutic simulation and when I try to mesh my envelope, the mesh fails for some reason with an error telling me that something is not acceptable.


      Can you help me please ?


      Best regards

      Zeynep

    • Erik Kostson
      Ansys Employee
      Hi
      Can you attach inline images in your next post, of the error message, the failed mesh, the geometry and a description of your model.

      Thank you

      Erik
    • aslzynperl
      Subscriber
      Here is my error.
    • Erik Kostson
      Ansys Employee
      I do not understand - translate that if you want someone to help since it is more likely that you will receive more response if you translate - also the more information your provide showing the model and the model tree the more likely it is that someone will be able to help.

      All the best of luck

      Erik
    • aslzynperl
      Subscriber
      The translation of my error is this : the surface mesh intersects or is close to intersecting, making it difficult to create a volume mesh. Please adjust the mesh size or geometry to solve the problem.

      And here is my model tree with the failed mesh.


    • Erik Kostson
      Ansys Employee
      The first thing to do is to try and use a much smaller element size see if that helps .

      Erik
    • Emperor
      Subscriber
      Salut pourquoi fais tu un maillage tetra et pas un hexa vu la simplicit├® de ta g├®om├®trie ? Tu devrais aussi r├®duire la taille des ├®l├®ments si tu restes en t├®tra


      Why do you make a tetra mesh and not a hexa mesh given the simplicity of your geometry? You should also reduce the size of the elements if you stay in tetra
    • aslzynperl
      Subscriber
      Salut ├ëtant une d├®butante absolue, je n'ai aucune id├®e de comment faire un maillage hexa. Tu pourrais me le dire stp ?

      Merci pour ta r├®ponse.
    • aslzynperl
      Subscriber
      Hey Erik
      I actually tried with a smaller element size but my computer isn't strong enough to run that kind of operation. I'm searching for the optimal result.

      Thanks for your help
    • aslzynperl
      Subscriber
      Plus, small sizes doesn't work I still got the exact same error.
    • Emperor
      Subscriber
      lorsque tu commentes, tu peux rajouter le symbole @ devant le nom pour que la personne re├ºoit directement une notification sinon il est compliqu├® de te r├®pondre directement.

      Vu que ta g├®om├®trie est un cube, il sera facile pour lui de mettre des ├®l├®ments hexa.
      -supprime la taille de corps que tu a rajout├®,
      -clic sur maillage
      -Dans d├®tail change la taille d'├®l├®ment par 0,5 par exemple ( tu dois utiliser la virgule et pas le point sinon ca ne marchera pas)
      -mets à jour ton maillage





    • aslzynperl
      Subscriber
      Merci pour le conseil, je l'essaie et je te fais un retour dès que possible.

    • aslzynperl
      Subscriber
      Re Alors j'ai essay├® ta m├®thode et j'ai toujours un maillage ├®chou├®.
    • Emperor
      Subscriber
      tu peux faire une capture de maillage ├®chou├® et aussi du d├®taille de maillage?
    • Emperor
      Subscriber
      et faudra faire gaffe quand tu utilises le @ faut taper le bon nom aussi
    • aslzynperl
      Subscriber
      Ceci est mon maillage. Pourtant il n'est pas un simple cube. C'est juste l'enveloppe d'un stator qui se trouve ├á l'int├®rieur. J'envoie un aper├ºu de ma g├®om├®trie ci-dessous.


    • Emperor
      Subscriber
      je comprends mieux pourquoi il ne marche pas. Il y'a un ├®l├®ment ├á l'int├®rieur. Ta structure du milieu contient t'elle des troues ? Tu as pens├® ├á nettoyer la g├®om├®trie dans SpaceClaim ?
      Si tu peux partager ton projet en joignant l'archive je pourrai regarder
    • aslzynperl
      Subscriber
      J'avais fait un "fault detection" sur Design Modeler mais il s'est av├®r├® qu'il n' y avait pas de souci. Est-ce qu'il y a d'autres moyens pour voir s'il y a des trous dans mon mod├¿le ?
    • Erik Kostson
      Ansys Employee
      Hi

      As we said because of the language not many will be able to help - from the image I see you model an electric motor (and nvh/acoustics on that) - for the acoustic domain only surround the casing not the inside teeth and brush of the motor (that is causing the issue with the mesh).
    • aslzynperl
      Subscriber

      That's ecatly what I'm working on. How can I do this please , Because I'm not much of a pro :)

      Thanks for your help
    • Emperor
      Subscriber
      Je n'utilise pas DesignModeler, j'utilise SpaceClaim. Il est donc possible de r├®parer la g├®om├®trie dans SpaceClaim. Mais ceci n'est qu'une hypoth├¿se que je propose, peut ├¬tre qu'il faut mener une autre action. Tout de m├¬me il est claire que c'est quelque chose sur la g├®om├®trie qui emp├¬che le maillage. Tu es sur une version Etudiante(je pense) dans ce cas tu es limit├® en nombre de n┼ôuds.
      Il y'a des m├®thode pour pouvoir mailler ├á bien une structure, dans un premier temps tu peux la d├®couper pour rendre la g├®om├®trie mappable et utiliser la topologie partag├®. Ce son des strat├®gie de maillage.
      Tu peux commencer ├á ne mailer que le boitier et pas la pi├¿ce qui est ├á l'int├®rieur, c'est cette pi├¿ce qui cause un probl├¿me sur le maillage. est plus sp├®cialiste que moi, il aura de meilleur conseil.

      ---------------------------

      I don't use DesignModeler, I use SpaceClaim. So it is possible to repair the geometry in SpaceClaim. But this is only a hypothesis I propose, maybe another action is needed. However it is clear that it is something about the geometry that prevents the mesh from working. You are on a Student version (I think) in which case you are limited in the number of nodes.

      There are methods to mesh a structure well, first you can cut it to make the geometry mappable and use the shared topology. These are the meshing strategies.

      You can start to mesh only the box and not the part inside, it is this part that causes a problem on the mesh. is more specialist than me, he will have better advice.
    • Erik Kostson
      Ansys Employee
      Hi

      So you should have an acoustic domain as shown here:
      What do you use for geometry prep., spaceclaim or?
      Erik
    • aslzynperl
      Subscriber
      Exactly spaceclaim @ekoetotson

    • Erik Kostson
      Ansys Employee
      Ok, I think when you do the air enclosure, just pick the outer faces of the emotor casing.

      Try that

      Erik
    • aslzynperl
      Subscriber
      I will work on it. I will tell you if it works or not.
      Thanks for your advice.
    • Erik Kostson
      Ansys Employee
      It is not working so it is tricky in SC - design modeler it should work (choose outer faces).

      Erik
    • aslzynperl
      Subscriber
      Ok thank you I'm working on it
    • Erik Kostson
      Ansys Employee
      Below are the steps on how to do this in SC (there might be more ways but this is the one I found working :)).

      Select the outer edges on one side of the emotor casing (see below).


      Copy paste - so ctrl+c and ctrl+v and we get curves (See below)


      Finally choose all curves and click on fill

      We now get a face of the casing cross section which we can pull/extrude.

      Finally create enclosure on this new part.

      The final is OK.


      That should now mesh easily since we do not have inside of the casing (we only need exterior casing surfaces for external sound radiation calcs.).




    • aslzynperl
      Subscriber
      But doesn't this modify my geometry ? I mean I also need the stator for a bunch of other calculations and if I modify my geometry like this, I won't have the same results right ?
    • Erik Kostson
      Ansys Employee
      This air domain is for the harmonic acoustic part . Of course for your harmonic repsonse you need the teeth and so on.

      This is very complex analysis, so I suggest you look through this webinar on how to do this :

      Search there are quite a few links

      Best of luck.

      Erik
    • aslzynperl
      Subscriber
      Thanks a lot for your help :)
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