Trimmed Mesh Cell Quality

alw7 · August 13, 2018, 12:15

Good Morning,

How come if you have a perfect cube and you use a trimmed mesh, you will never have all the cells at 100 % quality?

Thank you!

me3840 · August 13, 2018, 20:55

You can certainly mesh a perfect (or very, very closer to it) cube with the trimmer. But you need your cube to align perfectly with the octree mesh.

The trimmer autogenerates a background mesh over objects and then 'trims' out the cells that are not in desired volumes. If the desired volume is perfectly aligned with the background mesh, then you get nearly exactly the perfect background mesh.

alw7 · September 14, 2018, 14:10

Thank you, how do I perfectly align the desired volume with the background mesh then?

fluid23 · September 17, 2018, 12:16

I believe that would be a structured mesh and you cannot do that with star-ccm, currently. You would have to mesh using a 3rd party software and import that.

I could be wrong.

SoAero · September 17, 2018, 13:30

You can use "Perform Mesh Alignment" in the trimmer to accomplish what you are describing. The wrapper has this same functionality.

You can use that alignment point as an anchor for the bounding box of the geometry. Look at the documentation for more information.

me3840 · September 18, 2018, 00:28

Quote:

Originally Posted by SoAero

You can use "Perform Mesh Alignment" in the trimmer to accomplish what you are describing. The wrapper has this same functionality.

You can use that alignment point as an anchor for the bounding box of the geometry. Look at the documentation for more information.

This will allow you to align the mesh at a particular point, but IMO a superior method is to have the trimmer use a particular coordinate system. You can define a coordinate system under the trimmer mesher object in an operation or continuum. The coordinate system approach allows the background mesh to have any orientation and position.

Quote:

Originally Posted by fluid23

I believe that would be a structured mesh and you cannot do that with star-ccm, currently. You would have to mesh using a 3rd party software and import that.

I could be wrong.

STAR-CCM+ can make structured meshes via the Directed Mesher. The solver will still treat them as unstructured. They'll have great quality though.

August 13, 2018, 12:15	Trimmed Mesh Cell Quality	#1
alw7 New Member Indiana (IN) Join Date: Apr 2018 Posts: 6 Rep Power: 8	Good Morning, How come if you have a perfect cube and you use a trimmed mesh, you will never have all the cells at 100 % quality? Thank you!

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August 13, 2018, 20:55		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	You can certainly mesh a perfect (or very, very closer to it) cube with the trimmer. But you need your cube to align perfectly with the octree mesh. The trimmer autogenerates a background mesh over objects and then 'trims' out the cells that are not in desired volumes. If the desired volume is perfectly aligned with the background mesh, then you get nearly exactly the perfect background mesh.

September 14, 2018, 14:10		#3
alw7 New Member Indiana (IN) Join Date: Apr 2018 Posts: 6 Rep Power: 8	Thank you, how do I perfectly align the desired volume with the background mesh then?

September 17, 2018, 12:16		#4
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 18	I believe that would be a structured mesh and you cannot do that with star-ccm, currently. You would have to mesh using a 3rd party software and import that. I could be wrong.

September 17, 2018, 13:30		#5
SoAero New Member Owen Join Date: Aug 2018 Posts: 20 Rep Power: 8	You can use "Perform Mesh Alignment" in the trimmer to accomplish what you are describing. The wrapper has this same functionality. You can use that alignment point as an anchor for the bounding box of the geometry. Look at the documentation for more information.