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[ICEM] ICEM hexa bunching question: number of nodes and pre-mesh display

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Old   April 5, 2021, 04:55
Default ICEM hexa bunching question: number of nodes and pre-mesh display
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zuheyr alsalihi
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Happy Easter!
Please do forgive my silly question but I am baffled: newcomer to ICEMCFD, in a simple 2D mesh with Hexa, I give 3 nodes along an edge in the bunching, and the pre-mesh plot shows me 11 grid points along that edge. Please tell me what is happening? I checked the manual:
Nodesspecifies the number of nodes along the edge. The number may be modified using the up and down arrows or by entering a number in the field.


I give 3 nodes, pre-mesh plots 11? Thanks for reading!

Kind regards and best wishes!
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Old   April 6, 2021, 09:20
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Hello,

Could you please attach a photo of the line with 11 nodes, and a picture of the GUI where you specify the number of nodes and the mesh law?
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Old   April 6, 2021, 10:12
Default Photos of the bunching and pre_mesh
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zuheyr alsalihi
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Thank you *so much*

I attach screenshots which I hope are visible.
I can send pictures by other means as well if not clear. I also tried hyperbolic etc, the same. The pre_mesh picture is from
What is so critical to me is what pre_mesh is plotting really? So important to understand this.

Thank you so much! Best, Zuheyr
Attached Images
File Type: jpg bunching.jpg (70.5 KB, 12 views)
File Type: jpg pre_mesh.jpg (164.3 KB, 11 views)
File Type: jpg bunching_hyperbolic.jpg (149.4 KB, 9 views)

Last edited by zuheyr; April 6, 2021 at 10:17. Reason: Attached uniform and hyperbolic bunching edge informations
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Old   April 6, 2021, 15:22
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Sebastian Engel
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Hi Zuheyr,


it is likely, that you blocks have a refinement level which is not 1.


In the meshing parameters menu (3rd from the left) you show in your screenshots there is a button to show and modify the refinement levels of blocks(5th from the left).
You likely need to set the refinement back to 1 for the respective blocks.


Best,
Sebastian
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Old   April 6, 2021, 15:49
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zuheyr alsalihi
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Sebastian you were right! It was 0.5!!



In fact this brings about a very important concern of mine:
I need to make a 3 times refinable mesh for refinement study. it is a 2D mesh.



What is the best way of achieving this?



There is also a possibility to set a fixed multigrid level, such as 3.


I am grateful to you! Thank you.



Best wishes, Zuheyr
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Old   April 6, 2021, 16:08
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Sebastian Engel
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I think, I don't fully understand what you mean.

Quote:
3 times refinable mesh
Assuming you strictly ask for refineABLE: When you have an existing mesh, you can refine a mesh at any later point in time. Of course, you can choose to either use a refinement level of 3 everywhere, or increase the node count globally by applying the multiplication of 3. The latter changes the node count permanently, though. You'll find the latter feature also in the mesh parameters menu (I think it was the first tab of the menu, maybe second.. I don't know by heart, but i know you cant miss it from those two).

Quote:
There is also a possibility to set a fixed multigrid level, such as 3.
It is totally valid to have every block at the same refinement level, such as 3, it's just unusual. Using refinements instead of changing the node count is good practice in term of reversibility. It's easy to change the refinement level, reversing every node count not so much.


Consider refinement levels as a post processing step of the edge parameters---they only have a one-way dependency to the edge parameters.
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Old   April 6, 2021, 16:16
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That is a perfect clear explanation. Thank you very much. Best wishes, Zuheyr
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Old   April 12, 2021, 04:03
Default Coarsening is also possible?
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Quote:
Originally Posted by bluebase View Post
I think, I don't fully understand what you mean.

Assuming you strictly ask for refineABLE: When you have an existing mesh, you can refine a mesh at any later point in time. Of course, you can choose to either use a refinement level of 3 everywhere, or increase the node count globally by applying the multiplication of 3. The latter changes the node count permanently, though. You'll find the latter feature also in the mesh parameters menu (I think it was the first tab of the menu, maybe second.. I don't know by heart, but i know you cant miss it from those two).

It is totally valid to have every block at the same refinement level, such as 3, it's just unusual. Using refinements instead of changing the node count is good practice in term of reversibility. It's easy to change the refinement level, reversing every node count not so much.


Consider refinement levels as a post processing step of the edge parameters---they only have a one-way dependency to the edge parameters.

I ran into a problem that perhaps you can please help: Can I use the bloack refinement you mention in the meshing parameters menu, the 5th icon, by using a refinement level less than 1? Strangely when I was mistakenly using 0.9, as you have caught, it was working, when I make a good mesh and want to *coarsen* it, I get a cryptic error message saying the factor must be positive!

Can I do coarsening? Thank you so much for reading!
Zuheyr
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Old   April 12, 2021, 15:39
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Quote:
Originally Posted by zuheyr View Post
I ran into a problem that perhaps you can please help: Can I use the bloack refinement you mention in the meshing parameters menu, the 5th icon, by using a refinement level less than 1? Strangely when I was mistakenly using 0.9, as you have caught, it was working, when I make a good mesh and want to *coarsen* it, I get a cryptic error message saying the factor must be positive!

Can I do coarsening? Thank you so much for reading!
Zuheyr
Hello,

I have had this problem before and found a way to solve it. You need to input a fraction (i.e. 1/2) rather than a decimal (i.e. 0.5).
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Old   April 14, 2021, 08:13
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Dear Kira,

Thank you, you once again saved me. Although much to my surprise I unhappily discovered in these forums that refinement is creating hanging nodes whatever they may be, which Fluent ignores but i am using a normal solver and it does not. This will be another thread I will ask for help.

I just mention it here for the unawares like me.

Kindest regards, Zuheyr
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Old   April 14, 2021, 09:55
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Sebastian Engel
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Hi Zuheyr,


Kira knows your struggle for sure. =) Maybe this thread is interesting to you, too: Different Levels of Refinement in Adjacent Blocks


Best,
Sebastian
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Last edited by bluebase; April 14, 2021 at 10:09. Reason: wrong link
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Old   April 14, 2021, 10:53
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Quote:
Originally Posted by bluebase View Post
Hi Zuheyr,


Kira knows your struggle for sure. =) Maybe this thread is interesting to you, too: Different Levels of Refinement in Adjacent Blocks


Best,
Sebastian
That's for sure, Sebastian. One of the upsides of my struggles is that I am able to help others.
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