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Mesh resolution to capture thin solid regions

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Old   December 19, 2013, 00:38
Default Mesh resolution to capture thin solid regions
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Akshay Kumar
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Hey Guys

I have a solid region with a small thickness. How do i make sure that the mesh captures these thin regions. Interestingly even when I have a super fine mesh(order of 10 mil), it does not capture these solids. Is there any special way?

Thanks
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Old   December 22, 2013, 01:57
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Jeff Burnham
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There are three ways:

1) make the mesh cells small enough that there are 3 cells across the thinnest region.

2) if the region is too thin for (1), then consider using a baffle (which is 2-D, and lies on the grid lines) instead of a component (which is 3-D, and needs to be resolved by cells). Note that because baffles snap to the nearest gridline, they will make stair-steps if they're angled diagonal to the mesh. Complex baffles can be imported from .stl files in v10.1 and later.

3) if possible, consider making the regions thicker in CAD. For example, extrude topography surfaces downward. Make sure to re-check and fix the .stl file after you export it, like maybe with netfabb Studio.
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Old   December 23, 2013, 00:29
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Akshay Kumar
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Thanks Burnham but....

The baffles option will not work for me because my model is a moving object. And I don't think I can increase the thickness considering my case. So the only option left is to resolve it through a finer mesh.
I've attached an image(notice it has a small thickness). Now how can I setup mesh planes(grid points) for such a geometry so that I can capture the entire model. Is there any quick way for such situations?

Akshay
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Old   December 23, 2013, 00:31
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MultiBlocks!!?? One block contained in another? Will that work?
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Old   December 23, 2013, 12:35
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Yes, you can nest finer blocks inside larger blocks. FLOW-3D will change the boundary condition in the nested block to "inter-block" type automatically. However, the nested blocks do not move, so they can't follow the moving object. Good luck.
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Old   December 24, 2013, 07:54
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Akshay Kumar
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I'll let you know what happens. And..
What is the usual cell count for complex meshes/physics used in Flow3D?
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Old   December 31, 2013, 11:38
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Cell count depends on how much memory you have. In general:

cell counts in the hundreds will run in seconds
cell counts in the thousands will run in minutes
hundreds of thousands of cells run in hours or days
millions of cells take days or weeks to run
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