3D mesh around a co...
 

3D mesh around a column  

 

saberman12
(@saberman12)
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September 12, 2019 8:26 am  

Hi, I am trying to 3D mesh the boundary around my column which is going to be my air domain for my blast simulation. I am able to mesh my column with no issue but I am facing trouble trying to mesh the air as my column is slightly tilted like a trapezoid. I have attached a picture, showing my model from the top view. I hope you are able to share your knowledge of meshing and thanks for the time.

1568273192-Capture.png

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Negative Volume
(@negativevolume)
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September 12, 2019 1:40 pm  

The easiest method would be a tetrahedral fill from an enclosed mesh. You would do this by going to 3D -> tet mesh -> select by elements -> then select all of the elements from the column and the enclosed boundary and specify a mesh size.

A hexahedron mesh will be much harder but will require you to divide the “air” into 3 verticals columns (left edge of column, right edge of column) 

Will a tetrahedral mesh work for you?


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saberman12
(@saberman12)
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September 13, 2019 1:52 am  

I would as much as possible use hexahedron mesh for this simulation and I hope you are able to enlighten me how I can achieve it. I had tried some youtube video methods but haven't been successful in my attempts.


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Negative Volume
(@negativevolume)
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September 17, 2019 1:37 pm  

@saberman12

If you want to mesh with hexahedrals then you are going to need a 3D geometry of that boundary condition that you provided. Do you have that already? 


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saberman12
(@saberman12)
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September 18, 2019 6:06 am  

@negativevolume

I have the 3D model of the drawing I provided.


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Negative Volume
(@negativevolume)
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September 18, 2019 11:54 pm  

@saberman12

Okay perfect. So the first thing you will need to do is make sure that the geometry is a solid, not just surfaces. You can check this by going into Tool -> Delete -> changing the selection box to Solid and seeing if you can select your geometry. If you cannot, make sure the surfaces are enclosed and go to Geometry -> Solids -> Bounding Surfaces and select all surface to create solids. 

Now that you have solids, you need to split them so that Hypermesh can hex mesh them in an orderly fashion. You can trim the solids in Geometry -> Solid Edit -> and you have a variety of trim options. My suggestion would be to trim the "air" part with the top edge of the cylinder. You can try to do this by using this edge to trim directly upwards or along the angle of the cylinder. I would try the first way to start. 

Try the "with sweep lines" option under the "trim with lines" tab. Select the air solid and then the top edge of the cylinder as the line. If you cannot select the edge as a line you can create a line from that edge in Geometry -> Lines, but you should be able to use an edge. Then "sweep to: by a vector" and click the down arrow next to N1 N2 N3 and change it to your vertical axis. It should extrude that edge upwards and cut through the solid. 

Once that is done, try to hex mesh it in 3D -> Solid Map -> Multi Solids -> select the air solid and select the outer cylinder surface and top cylinder surface as the source hint and then select the outer surfaces of the box as the destination hint. This may or may not work the first try but try changing the source and destination surfaces if not and you can try the other 3D meshing tabs to see if one works. But this would be my first thought on how to do this. 

Let me know if you run into trouble. 


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saberman12
(@saberman12)
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October 9, 2019 7:49 am  

Hi, thanks for the suggestion. I tried your suggestion but got stuck halfway through. However, I was able to mesh my model with a different method. Firstly, I modelled the 2D model of my drawing. Next, I assigned nodes on the edges and split the areas around the model into triangles, rectangles and squares. I assigned the areas with Surface and then 2D automesh the areas. I then used 3D drag to drag my 2D mesh into 3D mesh.  Still, I appreciate the help you offered me. Thanks.


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Negative Volume
(@negativevolume)
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October 9, 2019 1:23 pm  

@saberman12

Great to hear you got it figured out! Yeah 3D drag is great for rectangular geometries like that.


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