How to prevent SPH Fluid Falling Through Welds

Crashphys
Crashphys Altair Community Member
edited October 2020 in Community Q&A

Hi,

 

For the model info please see attached. If you run the .h3d, you will notice there are SPH particles falling through the side of the hopper car. This is because I have RBODYs connecting the side walls to the floor, acting as MPCs, as shown in the picture. Although I understand the physics are definitely very messed up, considering that I have only some 50 SPH particles each weighing hundreds of kg, my main concern right now is to prevent these particles from falling through the edges on the side. Using shell elements in that region results in very high aspect ratio elements, increasing my minimum timestep by a factor of 10.

 

Can anyone advise how to 'seal' this region off so that it acts as a wall, preventing SPH particles from passing through without the use of shell elements?

 

Thanks in advance!

 

image.png.df898fa13b80f131a409185325751cf3.png

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Answers

  • Crashphys
    Crashphys Altair Community Member
    edited April 2019

    SOLVED

     

    In case anyone ever stumbles upon this, there's really no way to get around it. You have to find some way to make the shell elements merge. I did this by painstakingly deleting and redoing specific elements one by one using mesh->create->2D->Element and selecting nodes one by one. This process really sucks and takes a long time, so if anyone knows a better way feel free to post.

     

    Cheers

     

    Also make sure to add those newly created elements to your contact surface so that you don't waste 10 minutes like I just did :)/emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited April 2019

    You wasted a lot more time because you didn't use all the available methods :D/emoticons/default_biggrin.png' srcset='/emoticons/biggrin@2x.png 2x' title=':D' width='20' />

    You could equivalence the nodes by specifying proper tolerance


    or create the mesh in the gap by 2D>ruled


     

  • Crashphys
    Crashphys Altair Community Member
    edited April 2019

    I actually ended up using the above methods to solve the problem. In this case, equivalence was causing a few problems since the gap distance was very large. The tolerance had to be so high that other parts of the mesh were damaged. Ruled mesh would have been OK, but you would still have to delete individual elements and remake them. There probably was a faster way than what I did, but the process still sucks... LOL

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