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Cylinder hex mesh refined close to the wall

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Old   July 5, 2022, 06:49
Default Cylinder hex mesh refined close to the wall
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Hello all, I was wondering for a simple pipe (cylinder) geometry, how to have the mesh coarse in the centre and finer close to the wall, using hex mesh only?

Thanks!

EDIT: by the way I am looking for something like this:
https://www.cfd-online.com/Forums/at...mesh_ogrid.jpg

But I am not using IcemCFD, I am using Ansys Fluent mesher, and I tried setting the same parameters as in the picture but with poor results...
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Old   July 5, 2022, 07:39
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Quote:
Originally Posted by Benzouz View Post
Hello all, I was wondering for a simple pipe (cylinder) geometry, how to have the mesh coarse in the centre and finer close to the wall, using hex mesh only?

Thanks!

EDIT: by the way I am looking for something like this:
https://www.cfd-online.com/Forums/at...mesh_ogrid.jpg

But I am not using IcemCFD, I am using Ansys Fluent mesher, and I tried setting the same parameters as in the picture but with poor results...
Hi, just to be sure, are you using ANSYS meshing or Fluent meshing? ANSYS meshing is the general purpose one and looks different to Fluent GUI. Fluent meshing looks the same as Fluent solver GUI. I'm asking because the answer would be different depending on what mesher you use.
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Old   July 5, 2022, 07:57
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I believe I might be using the Ansys meshing, it seems to be called CFD PrepPost
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Old   July 5, 2022, 08:20
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Quote:
Originally Posted by Benzouz View Post
I believe I might be using the Ansys meshing, it seems to be called CFD PrepPost
Alright, so use face meshing on one end face of the cylinder and d a sweep mesh. You'll have the mesh as you have shown in the image.


If you wanna do it manually, take one end face of the cylinder, put a square in the middle, and extend the squares vertices perpendicularly to the edge of cylinder face. This way you can get a mesh exactly like the image you shared.
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Old   July 5, 2022, 08:35
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Is there any parameter I can set in the Face meshing? There isn't much I seem to be able to change:



So I tried using the sweep method and face meshing (on both inlet and outlet faces) but I'm not able to get inflation layers, even in the global options of the mesh. I get something like this:

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Old   July 5, 2022, 08:59
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Quote:
Originally Posted by Benzouz View Post
Is there any parameter I can set in the Face meshing? There isn't much I seem to be able to change:



So I tried using the sweep method and face meshing (on both inlet and outlet faces) but I'm not able to get inflation layers, even in the global options of the mesh. I get something like this:

If the inflation layer thing doesn't work, go with the manual method i told you about, ssplitting faces in geometry and then meshing it. There you can apply edge sizing and put a boundary layer.
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Old   July 11, 2022, 13:18
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I tried manual method and I've had some good results by following a tutorial (https://youtu.be/8_osCXZjv_g) but I don't get the same when applying it to my geometry.

Here's how it looks with the cylinder of the tutorial:


And here's how it looks like with my geometry:


The two differences between my geometry and that of the tutorial are the dimensions of the middle square compared to the diameter of the pipe (it's not really possible to get the same ratio) and the fact that my geometry is not just a cylinder but a pipe with a bend.

Anyone would know how to fix that?
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Old   July 14, 2022, 03:16
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in tutorial there are more points on middle square edges

also distances between points on exteral circle are not even, this is the difference
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Old   July 14, 2022, 05:41
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Quote:
Originally Posted by Benzouz View Post
I tried manual method and I've had some good results by following a tutorial (https://youtu.be/8_osCXZjv_g) but I don't get the same when applying it to my geometry.

Here's how it looks with the cylinder of the tutorial:


And here's how it looks like with my geometry:


The two differences between my geometry and that of the tutorial are the dimensions of the middle square compared to the diameter of the pipe (it's not really possible to get the same ratio) and the fact that my geometry is not just a cylinder but a pipe with a bend.

Anyone would know how to fix that?
you need to apply edge sizing on the edge of the tube face shown in the image. Currently the mesh resolution is not sufficient to properly render the curvature of the pipe walls.
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Old   July 14, 2022, 07:33
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Thank you for your answers. I indeed had manged to solve this issue by applying an edge sizing on the outer part of the cylinder. But now I notice I am facing another issue which I think has to do with the fact that I am not using the same ratio of the size of the square compared to the cylinder diameter. In this case here is what I get:



While if I apply the same ratio it works fine. By the way I had created another thread on the meshing subforum to talk about this problem because I noticed I was not on the right subforum. Feel free to close this thread and reply on the other one (O-grid mesh on cylinder with 90 degree angle not pretty) or vice-versa.

Thanks again for your help!
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Old   July 14, 2022, 07:46
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Quote:
Originally Posted by Benzouz View Post
Thank you for your answers. I indeed had manged to solve this issue by applying an edge sizing on the outer part of the cylinder. But now I notice I am facing another issue which I think has to do with the fact that I am not using the same ratio of the size of the square compared to the cylinder diameter. In this case here is what I get:



While if I apply the same ratio it works fine. By the way I had created another thread on the meshing subforum to talk about this problem because I noticed I was not on the right subforum. Feel free to close this thread and reply on the other one (O-grid mesh on cylinder with 90 degree angle not pretty) or vice-versa.

Thanks again for your help!
try using number of division for edge sizing instead of element size. You can also apply edge sizing on the edges extending from the square to the walls. Play around with number of division and bias in edge sizing to get a good mesh.
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