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[ywang2524]

Hi,

   There will be some unwanted mesh outside the original geometry after generating mesh using tetrahedron independent method. How can I avoid this problem? Thanks!

[ywang2524]

[Keyur Kanade]

which tool you are using - ICEM or Workbench Mehsing?

 

If it is WB Meshing, there must be some geometry there. Please go to SpaceClaim or DesignModeler and delete the geometry at that location. 

Regards,

Keyur

 

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[ywang2524]

Thanks for your reply. I am using WB meshing, but I don't think there is some geometry there, since if I change the mesh size, the shape and position of the mesh left outside will be different. Will there be some other causes? 

Thanks!

[Rob]

Looking at all the random clustering of cells there's something inside the pipe, you have a very uneven surface or the geometry is slightly corrupt. How did you create it?

[ywang2524]

I used Solidworks. Sorry the graph is not very clear, the clustering of cells is caused by 5 helical inner tubes.es.

[Keyur Kanade]

can you please slice a small part of this geometry and try to mesh. 

I can see it is around 0.25m. 

can you please slice it to say 0.1m and try to mesh it. 

also please change sizing. 

https://www.youtube.com/watch?v=w4q6q8nKF3U

Regards,

Keyur

 

If this helps, please mark this post as 'Is Solution' to help others.

Guidelines on the Student Community

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[ywang2524]

Hi,

    Thanks for your suggestion and the video! I have tried changing the size, now the unwanted mesh disappeared, but I got a very large amount of elements with a minimum orthogonal quality as 6.5e-2. How to slice the mesh? Should it be done in Meshing or DesignModeler? Thanks so much!

     

[Keyur Kanade]

check this

https://www.youtube.com/watch?v=wAEqemb-yL8

Regards,

Keyur

 

If this helps, please mark this post as 'Is Solution' to help others.

Guidelines on the Student Community

How to access ANSYS help links

 

[ywang2524]

Thanks a lot! I will check the video and try to regenerate the mesh. But for this very large mesh, I applied non conformal periodic boundary conditions to the shell side inlet and outlet, the following error happened and the case can not be solved. How to deal with this kind of problem? Does it have any thing to do with the non conformal periodic boundary conditions?

[Keyur Kanade]

if issue of unwanted mesh outside geometry is resolved, can you please mark this 'is solution' and create a new post for new question. 

it will help others on forum. 

Regards,

Keyur

 

If this helps, please mark this post as 'Is Solution' to help others.

Guidelines on the Student Community

How to access ANSYS help links

 

 

[ywang2524]

The unwanted mesh problem can be solved by decreasing the mesh size, but then there comes the large mesh problem, more than 18 million cells...Is there anything I can do to reduce the cell number?

For now, mesh can not be generated by patch conforming method under these settings, will patch conforming method do a better job than patch indenpdent method?

Thanks!

[Rob]

The problem looks to be that the cell size you'd used was bigger than the gaps, patch independent will let the mesh deviate from the surface to avoid the problem.  I can see it's a heat exchanger of some sort, what are you trying to find out in the results? 

[ywang2524]

I am trying to find out the correlation between Nu, friction factor and Re for this heat exchanger. So I can increase the size of gaps a little instead of using smaller mesh to avoid the problem? Thanks!

[Rob]

Yes, if that won't mess up your results. Also have a look at periodic boundaries, if you shorten the section (and only have flow on the shell-side) mesh count will be less of an issue. 

[ywang2524]

Thanks! Changing the size of gaps worked.