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Population Balance Modeling (DQMOM setup)

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Old   February 13, 2014, 23:08
Default Population Balance Modeling (DQMOM setup)
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Manjunath
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Hello Fluent users,

My problem has gas and liquid phases with gas as my secondary phase in a stirred tank and I am using PBM to investigate the size distribution. What the three DQMOM phases to be used in the DQMOM and how are they defined? Does the three phase have to do with the initial particle or bubble size distribution? Is it necessary to define three phases? (Fluent throws a pop up window saying three DQMOM phases must be selected). I could not find much information on model setup in the theory and user guide.

Thanking for the help in advance.

Regards,
Manjunath
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Old   August 25, 2014, 04:15
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Ouyang Zailong
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Quote:
Originally Posted by manjunath View Post
Hello Fluent users,

My problem has gas and liquid phases with gas as my secondary phase in a stirred tank and I am using PBM to investigate the size distribution. What the three DQMOM phases to be used in the DQMOM and how are they defined? Does the three phase have to do with the initial particle or bubble size distribution? Is it necessary to define three phases? (Fluent throws a pop up window saying three DQMOM phases must be selected). I could not find much information on model setup in the theory and user guide.

Thanking for the help in advance.

Regards,
Manjunath
Hi Manjunath!

I intend to use eulerian approach coupling with PBM model to obtain local BSD in a tank, but i am running into issues on QMOM/DQMOM setup in fluent too. Could you tell me the specific mean on setting three DQMOM phases and how to initial the moments on inlet boundary if you have solved your problems.

Best regards.
waouyouy
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Old   September 29, 2014, 20:10
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Eduardo da Rosa
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Quote:
Originally Posted by waouyouy View Post
Hi Manjunath!

I intend to use eulerian approach coupling with PBM model to obtain local BSD in a tank, but i am running into issues on QMOM/DQMOM setup in fluent too. Could you tell me the specific mean on setting three DQMOM phases and how to initial the moments on inlet boundary if you have solved your problems.

Best regards.
waouyouy
Hi Ouyouy! Did you solve that problem? I have the same problem.

Regards.

Eduardo
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Old   October 16, 2014, 05:38
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Originally Posted by eduardors View Post
Hi Ouyouy! Did you solve that problem? I have the same problem.

Regards.

Eduardo
Hi Eduardo, sorry for replying so late!
I have adopted QMOM method for PBM solution, and from the postprocessing, some unexpected results were acquired. Reasons account for that situation i guess show as follows:
first, values of the gas inlet boundary initial moments may set incorrectly(i set these values based on the volume fraction(0.03) of gas phase and bubble mean size(0.003m), such as, m3 = 0.03, m2 = 10, m1= 3333, ... );
secondly, the sequence of caculation: 1, single phase flow field; 2, coupling PBM. however, i am not sure it is correct or not.
thirdly, models for breakage and aggregation are crucial for the results.
--------------------------------------------------------------------
i hope we can discuss and learn about PBM together!
Best regards.
waouyouy
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Old   October 16, 2014, 13:35
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Quote:
Originally Posted by waouyouy View Post
Hi Eduardo, sorry for replying so late!
I have adopted QMOM method for PBM solution, and from the postprocessing, some unexpected results were acquired. Reasons account for that situation i guess show as follows:
first, values of the gas inlet boundary initial moments may set incorrectly(i set these values based on the volume fraction(0.03) of gas phase and bubble mean size(0.003m), such as, m3 = 0.03, m2 = 10, m1= 3333, ... );
secondly, the sequence of caculation: 1, single phase flow field; 2, coupling PBM. however, i am not sure it is correct or not.
thirdly, models for breakage and aggregation are crucial for the results.
--------------------------------------------------------------------
i hope we can discuss and learn about PBM together!
Best regards.
waouyouy
Thank you for you reply! Actually my difficulty now is find models for breakage and aggregation.

Are you using granular theory to characterize the bubbles?
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Old   October 17, 2014, 09:03
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Originally Posted by eduardors View Post
Thank you for you reply! Actually my difficulty now is find models for breakage and aggregation.

Are you using granular theory to characterize the bubbles?
no, i think granular theory may not suit for describing bubbles.
in addition, do you think the initial moments i defined above on gas inlet are correct?
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Old   October 17, 2014, 09:35
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Originally Posted by waouyouy View Post
no, i think granular theory may not suit for describing bubbles.
in addition, do you think the initial moments i defined above on gas inlet are correct?
Yes, I think it can be correct. What unexpect results did you get?
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Old   October 18, 2014, 07:02
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Originally Posted by eduardors View Post
Yes, I think it can be correct. What unexpect results did you get?
problems were the distribution of bubble size:
i use the steady state for simulation, and with the calculation going on, more and more bubbles are reach the max size which set in the pop model; at last, this situation will be spread to the whole tank.(see the pictures attached)
100_steps.png

300_steps.jpg

900_steps.png

apparently, this is nonphysical, but still i can not find the solution. so do you have some suggestions?
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Old   October 23, 2014, 13:13
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Quote:
Originally Posted by waouyouy View Post
problems were the distribution of bubble size:
i use the steady state for simulation, and with the calculation going on, more and more bubbles are reach the max size which set in the pop model; at last, this situation will be spread to the whole tank.(see the pictures attached)
Attachment 34446

Attachment 34447

Attachment 34448

apparently, this is nonphysical, but still i can not find the solution. so do you have some suggestions?
Hey! Sorry for replying so late. In this case I would try a transient state with a slow step to observe how the system behave in the beginning of operation. In some cases in steady state the model converges to a wrong result or even doesn't converge. Let me know if it changes in transient formulation, I always like to learn more and more.

Best regards.
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Old   October 25, 2014, 02:19
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Originally Posted by eduardors View Post
Hey! Sorry for replying so late. In this case I would try a transient state with a slow step to observe how the system behave in the beginning of operation. In some cases in steady state the model converges to a wrong result or even doesn't converge. Let me know if it changes in transient formulation, I always like to learn more and more.

Best regards.
Okay, i will try it again using transient state,
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Old   February 23, 2015, 03:09
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Hi, waouyouy.

Did you use 4 moments instead of 6 moments?

Can you explain why do you use it?

and the values,(m3,.....m0), are initial conditions or boundary condition value??
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