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December 7, 2012, 11:35 |
32G memory still not enough?
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#1 |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
The most powerful desktop I can access has 32GB memory.
but I still hit the limit when I try to mesh the geometry to get y+=1. I also tried to use coarse mesh and split the prism to get y+=1. However, that gives me very poor quality mesh. Could anybody give me some suggestions? |
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December 7, 2012, 14:11 |
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#2 |
Senior Member
Christoph
Join Date: May 2011
Location: Germany
Posts: 182
Rep Power: 17 |
which kind of simulation, how many elements (total) etc.?
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December 7, 2012, 14:23 |
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#3 |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
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December 7, 2012, 17:14 |
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#5 |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
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December 7, 2012, 18:20 |
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#6 |
Senior Member
Christoph
Join Date: May 2011
Location: Germany
Posts: 182
Rep Power: 17 |
Why do you use RSM?
This model is very complex and difficult to resolve numerical. But anyway.....140 M cells?!!! That's definitely too much for 32GB |
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December 7, 2012, 18:46 |
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#7 | |
Senior Member
Join Date: Dec 2009
Posts: 131
Rep Power: 19 |
not sure if the fluent solver is the same, but the CFX solver best practice guideline states
Aspect ratios away from the boundary layer should stay below 50. For well resolved boundary layers at high Re numbers, the near-wall aspect ratios can be of the order of 10^5-10^6. Then, of course, you need to use the double precision solver. The only issue this causes is the quality reports that are run flag this as a poor mesh. Quote:
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December 7, 2012, 23:58 |
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#8 | |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
Quote:
particle deposition rate would be high (wrong) if y+>3. |
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December 8, 2012, 00:51 |
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#9 |
Super Moderator
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which RSM model you are using? It has been shown repeatedly that RSM model is not always better than the two equation models.
Which effect you want to model with the RSM model? How many no. of layers you are using in boundary layer and why? What about the steam-wise resolution? It looks like to me a DNS mesh !!! BTW what is the Reynolds number you are trying to model? |
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December 8, 2012, 23:36 |
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#10 | |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
Quote:
I used Fluent RSM with enhanced wall function as I said the particle deposition rate would be high with k-e model because of the over prediction of velocity normal to the wall. right now, I just arbitrarily choose 3 layers. I am sorry I do not quite understand what is steam-wise resolution |
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December 8, 2012, 23:42 |
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#11 | |
Super Moderator
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Quote:
Only three layers in boundary layer? What is the maximum aspect ratio? Did you try the SST model with enhanced wall functions and curvature correction. You will almost get the same behaviour |
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December 10, 2012, 16:25 |
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#12 | |
New Member
Guan
Join Date: Dec 2011
Location: US
Posts: 25
Rep Power: 14 |
Quote:
With k-e with enhanced wall function and coarser mesh, the results were not so good. I have not try SST. Do you mean the transitional SST? |
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December 10, 2012, 22:59 |
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#13 |
Super Moderator
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I think Fluent has also implemented different versions of SST model like curvature correction. But CFX has full range of those models.
Just try SST model with well resolved boundary layer and somehow coarse mesh in the other regions. |
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