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Bubble column simulation with Lift coefficient UDF |
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June 26, 2013, 04:55 |
Bubble column simulation with Lift coefficient UDF
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#1 |
New Member
Balraju
Join Date: Feb 2011
Location: Hyderabad,India
Posts: 11
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Hii ..
Iam doing two phase cfd simulations of bubble column in FLUENT.I want to study the effect of lift force,so i wrote UDF.when i running with UDF in FLUENT its getting divergence.While compiling UDF,its not showing any errors.How to overcome this problem?? Please suggest me. |
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June 29, 2013, 05:22 |
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#2 | |
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Join Date: Nov 2012
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Quote:
"f1=0.0105*pow(mod_etvos,3)-0.0159*pow(mod_etvos,2)-0.0204*mod_etvos+0.474;" This equation is Tomiyama' equation and the first coefficient is 0.00105 instead of .0105. Getting convergence by considering lift force is not simple in bubble column and you should have a look on solution controls and AMG solver. |
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June 30, 2013, 01:41 |
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#3 |
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Hossein
Join Date: Oct 2010
Location: Greensboro, NC, USA
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the problem of writing a UDF aside, did you obtain reasonable velocity distribution? because when I simulate a bubble column, every thing looks fine, except velocity. the inlet velocity is 0.1m/s (air) but after some time steps, the maximum velocity in the system goes to 1.1 m/s. it seems like a air jet in the inlet, so it messes every thing up
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Hossein Amini PhD student in Biochemical Engineering; Computational Science and Engineering department; North Carolina Agricultural and Technical State University |
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June 30, 2013, 06:58 |
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#4 | |
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Balraju
Join Date: Feb 2011
Location: Hyderabad,India
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Quote:
Yes,the first coefficient is 0.00105. In simulations iam getting usually "Divergence detected in AMG solver". How to handle this problem?? |
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June 30, 2013, 07:21 |
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#5 | |
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Quote:
Please have a look on following thread: http://www.cfd-online.com/Forums/flu...ying-lift.html |
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July 2, 2013, 03:25 |
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#6 | |
New Member
Balraju
Join Date: Feb 2011
Location: Hyderabad,India
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Quote:
Thank you for your help. I have started simulations with that idea,but after some iterations simulation getting divergence. The error is coming like this "turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 120589 cells ". Please help me to overcome this problem. Regards, Raju |
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July 6, 2013, 09:47 |
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#7 |
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You can consider one of the following things:
1. Change AMG solver coefficients 2. Run the simulation in laminar condition at first then switch to turbulent 3. Do initialization with best initial guess (this Is very important) |
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July 11, 2013, 10:19 |
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#8 |
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Balraju
Join Date: Feb 2011
Location: Hyderabad,India
Posts: 11
Rep Power: 15 |
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June 19, 2023, 09:36 |
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#9 | |
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Parthasarathy yuvaraj
Join Date: Apr 2023
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Quote:
im also having the same issues. did u find any solution? |
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