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January 6, 2013, 14:10 |
Low Flow Convergence Help
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#1 |
New Member
Ryan Persaud
Join Date: Nov 2012
Posts: 4
Rep Power: 13 |
Hey guys, need some help with convergence. The application involves a 3" inlet pipe with 52 m/s velocity discharged into a 26"X50" duct. The duct has a U-bend with a 20" outlet.
This is a very slow flow problem due to the large size of the duct. We are expecting the velocity at the outlet to be approximately 1 m/s. Used a surface monitor plot at the outlet to look at the velocity, and scaled residuals criteria of 1e-5. The velocity of the outlet appears to have approached a value, however the residuals are quite high. I ran 5000 iterations to exclude the effect of under relaxation factors. I have posted the plots below. Any suggestions, or direction on how to improve the model will be great. Thanks! residuals 5000.jpg velocity 5000.jpg |
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January 7, 2013, 00:13 |
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#2 |
Senior Member
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,672
Rep Power: 65 |
Seems like everything is okay except for residuals.
Have you tried a finer grid? What about discretization schemes, 2nd order upwind on all? |
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January 7, 2013, 11:23 |
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#3 |
New Member
Ryan Persaud
Join Date: Nov 2012
Posts: 4
Rep Power: 13 |
I am using a student version of Fluent so I'm limited to 500000 cells and I'm using 2nd order for everything. I'm also using the Simple solver....would using another one help? any other ideas?
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January 7, 2013, 23:59 |
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#4 |
Senior Member
SSL
Join Date: Oct 2012
Posts: 226
Rep Power: 14 |
It is better to use the simplest form (First Order).
It is obvious that the problem is with your mesh. Refine it and try to make a structured mesh. |
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