Hexpress, move hanging nodes

liyifei · September 17, 2015, 00:18

Hello,

I want to use Hexpress to generate unstructured mesh to make a computation on CFX, but there is always hanging nodes in the mesh. Hanging nodes are forbidden in CFX, so how can I move the hanging nodes in the mesh generated by Hexpress? If it's not possible to do so in Hexpress, what software I can use to complete this?

Thank you!

colinda1 · September 21, 2015, 03:37

Hi,
You could use HEXPRESS/Hybrid instead. With a full-hex mesh in HEXPRESS it is not possible to avoid the hanging nodes unless you do not make any local refinements in the adaptation step. In HEXPRESS/Hybrid it is possible to create a hex-dominant mesh without hanging nodes. The resulting mesh may have also tets, prisms and pyramids.

liyifei · September 21, 2015, 11:37

Thanks for your reply!
I'm a beginner with Hexpress and Hexpress/Hybrid. In my experience, I think mesh made by Hexpress has higher quality than that made by Hexpress/Hybrid.
So as you know, I can't generate mesh without hanging nodes only with Hexpress, is it right? How can I move the hanging nodes made by Hexpress? Any software suggest?
I do try to generate mesh with Hexpress/Hybrid, but the boundary layer is not as good as Hexpress, if I use this software, what can I do to make better mesh with it?
Thanks so much for your help!

colinda1 · September 21, 2015, 11:50

Indeed HEXPRESS makes high quality meshes but indeed always with hanging nodes if you put local refinements in your mesh (and most often you need to).

You write that your boundary layer in HEXPRESS/Hybrid is not so good as in HEXPRESS. Maybe it is possible to show some pictures of the problematic boundary layer? It is difficult to know what could be done to improve it without seeing the problem.

liyifei · October 7, 2015, 10:18

Hey colinda1, me again!
I have tried to modify the mesh recently, and the mesh is good enough to make the calculation.
But there is still some problems I can't handle. I'm sorry that I don't know how to upload a picture. I want to make unstructured mesh in a turbine passage, the internal mesh in turbine has two periodical surfaces. Can I make a 1:1 grid on the two periodical surfaces with Hybrid？
Thanks！

tdrerwann · October 12, 2015, 12:32

Hi,
Periodic matching is available in HEXPRESS but I understand from your previous posts that you want to avoid hanging nodes...
In HEXPRESS/Hybrid, periodic matching is expected for next year.

liyifei · October 12, 2015, 22:08

It's amazing that you know so much about these software.
Thanks for all your help!

September 17, 2015, 00:18	Hexpress, move hanging nodes	#1
liyifei New Member Join Date: Sep 2015 Posts: 5 Rep Power: 11	Hello, I want to use Hexpress to generate unstructured mesh to make a computation on CFX, but there is always hanging nodes in the mesh. Hanging nodes are forbidden in CFX, so how can I move the hanging nodes in the mesh generated by Hexpress? If it's not possible to do so in Hexpress, what software I can use to complete this? Thank you!

September 21, 2015, 03:37		#2
colinda1 Senior Member Colinda Join Date: May 2012 Location: Brussels Posts: 153 Rep Power: 14	Hi, You could use HEXPRESS/Hybrid instead. With a full-hex mesh in HEXPRESS it is not possible to avoid the hanging nodes unless you do not make any local refinements in the adaptation step. In HEXPRESS/Hybrid it is possible to create a hex-dominant mesh without hanging nodes. The resulting mesh may have also tets, prisms and pyramids. liyifei likes this.

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September 21, 2015, 11:37		#3
liyifei New Member Join Date: Sep 2015 Posts: 5 Rep Power: 11	Thanks for your reply! I'm a beginner with Hexpress and Hexpress/Hybrid. In my experience, I think mesh made by Hexpress has higher quality than that made by Hexpress/Hybrid. So as you know, I can't generate mesh without hanging nodes only with Hexpress, is it right? How can I move the hanging nodes made by Hexpress? Any software suggest? I do try to generate mesh with Hexpress/Hybrid, but the boundary layer is not as good as Hexpress, if I use this software, what can I do to make better mesh with it? Thanks so much for your help!

September 21, 2015, 11:50		#4
colinda1 Senior Member Colinda Join Date: May 2012 Location: Brussels Posts: 153 Rep Power: 14	Indeed HEXPRESS makes high quality meshes but indeed always with hanging nodes if you put local refinements in your mesh (and most often you need to). You write that your boundary layer in HEXPRESS/Hybrid is not so good as in HEXPRESS. Maybe it is possible to show some pictures of the problematic boundary layer? It is difficult to know what could be done to improve it without seeing the problem.

October 7, 2015, 10:18		#5
liyifei New Member Join Date: Sep 2015 Posts: 5 Rep Power: 11	Hey colinda1, me again! I have tried to modify the mesh recently, and the mesh is good enough to make the calculation. But there is still some problems I can't handle. I'm sorry that I don't know how to upload a picture. I want to make unstructured mesh in a turbine passage, the internal mesh in turbine has two periodical surfaces. Can I make a 1:1 grid on the two periodical surfaces with Hybrid？ Thanks！

October 12, 2015, 12:32		#6
tdrerwann New Member Erwann Join Date: Feb 2015 Posts: 7 Rep Power: 11	Hi, Periodic matching is available in HEXPRESS but I understand from your previous posts that you want to avoid hanging nodes... In HEXPRESS/Hybrid, periodic matching is expected for next year.

October 12, 2015, 22:08		#7
liyifei New Member Join Date: Sep 2015 Posts: 5 Rep Power: 11	It's amazing that you know so much about these software. Thanks for all your help!