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[GAMBIT] mesh to capture boundary layer

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Old   March 9, 2014, 05:50
Default mesh to capture boundary layer
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Hi, I want to capture the boundary layer developed in natural convection phenomena in a cube geometry with flux supplied at bottom of cube. I want more mesh near the bottom of cube and coarse mesh at top. I tried by creating two volumes and meshed separately but it doesn't work in fluent.

Please provide me with a solution. I would really appreciate your time and effort.Thanks!!
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Old   March 9, 2014, 09:17
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Hi,
you can use boundary layer:

http://combust.hit.edu.cn:8080/fluen...301.htm#mg0301

Or size functions:

https://www.sharcnet.ca/Software/Gam...ide/mg0502.htm

No need to create 2 volumes.

What does it mean "but it doesn't work in fluent"??

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Old   March 9, 2014, 09:44
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Hi Daniele, I tried using boundary layer mesh. I want to pack 1000 rows in a depth of say 15 units. But, Gambit crashes whenever I try to do that. I am able to pack 190 rows within depth of 5 units only with growth factor of 1. After that any change causes Gambit to crash. Why is that?

Heat flux must be supplied at bottom face of my geometry.But when I load the double volume mesh file, flux gets applied in the interior wall which I created to separate the two volumes. I defined the type of that wall as interior and also checked my grid and boundary conditions, but flux keeps getting applied to interior wall. That is the volume which I meshed densely doesn't get solved. Why is that?

Thanks!!
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Old   March 9, 2014, 09:52
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Maybe you have "problems" with hardware (low amount of ram or similar)..
So split your volume ("the big cube") by a face and let connected the 2 volumes, so that the face which divides the 2 volumes is shared by both volumes.
Don't assign any boundary condition to that internal face, it will automatically detected in fluent as an internal face.

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Old   March 10, 2014, 03:13
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Maxime Perelli
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As Daniele mentionned it sounds like a hardware issue.
You wrote that you were able to mesh your model with 190 rows. In this case how many cells do you have in your domain, and how much RAM do you have on your hardware?
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Old   March 10, 2014, 10:22
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Hi Daniele, I didn't assign any boundary condition to that internal face but still the flux gets applied to the top face instead of bottom face. I meshed the volume below the interior densely since I am supplying flux to bottom face only. I can't understand what is the problem.
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Old   March 10, 2014, 10:23
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Hi Max
I have 3,45,600 hex cells and my RAM is 4GB.
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Old   March 10, 2014, 13:02
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Quote:
Originally Posted by Arvin View Post
Hi Daniele, I didn't assign any boundary condition to that internal face but still the flux gets applied to the top face instead of bottom face. I meshed the volume below the interior densely since I am supplying flux to bottom face only. I can't understand what is the problem.
upload the cas file somewhere and I will look at it.
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Old   March 11, 2014, 01:34
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Quote:
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Hi Max
I have 3,45,600 hex cells and my RAM is 4GB.
If you are working on windows OS, there is no real 64-bit version of Gambit. That means Gambit is limited on RAM (especially if you are trying to mesh your domain on the fly, eg just one volume)
As Daniele mentionned, you may try to split your volume, for giving Gambit any chance to mesh your BL without crashing, for instance isolate your BL region as a volume and mesh it again with more than 190 rows)
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