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Different results using Mixture model for 5.4 version and 5.2a version

Posted Sep 9, 2019, 11:37 p.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD) Version 5.4 6 Replies

Shiuh-Hwa Shyu
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I am using Mixture to run for lubrication flow in journal bearing with cavitation. It is very interesting that when I used 5.2a version, I can get the correct answer. When I used 5.4 version, the result is simply wrong. I believe that 5.4 version has a problem in mixture model.

6 Replies Last Post Oct 21, 2019, 9:09 p.m. EDT
Shiuh-Hwa Shyu
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Posted: 6 years ago Sep 10, 2019, 6:48 a.m. EDT
Updated: 6 years ago Sep 10, 2019, 6:48 a.m. EDT

I have noticed that since 5.4, the eqations for mixture model have been different from the earlier version. Perhaps there is some issues involved in there. Don't have any problem for bubbly flow model.

I have noticed that since 5.4, the eqations for mixture model have been different from the earlier version. Perhaps there is some issues involved in there. Don't have any problem for bubbly flow model.
Shiuh-Hwa Shyu
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Posted: 6 years ago Sep 10, 2019, 9:07 a.m. EDT

I have found that it has something to do with the numerical diffusion. Still looking for appropriate set.

I have found that it has something to do with the numerical diffusion. Still looking for appropriate set.
Mats Nigam COMSOL Employee

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Posted: 6 years ago Sep 11, 2019, 4:52 a.m. EDT

Dear Shiuh-Hwa, The formulation for the mixture model was changed in v5.4. It is now formulated in terms of the volume-averaged velocity instead of the mass-averaged velocity used in prior versions. If you can share your model, we can check that it's consistently set up. Best regards, Mats Nigam

Dear Shiuh-Hwa, The formulation for the mixture model was changed in v5.4. It is now formulated in terms of the volume-averaged velocity instead of the mass-averaged velocity used in prior versions. If you can share your model, we can check that it's consistently set up. Best regards, Mats Nigam
Mohammad Faizan
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Posted: 6 years ago Oct 14, 2019, 2:31 a.m. EDT

Dear Shiuh-Hwa, Did you solve your problem?

Dear Shiuh-Hwa, Did you solve your problem?
Shiuh-Hwa Shyu
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Posted: 6 years ago Oct 14, 2019, 3:28 a.m. EDT
Updated: 6 years ago Oct 14, 2019, 3:31 a.m. EDT

Dear Mats Nigam and Mohammad Faizan

I did solve the problem. As I said, the numerical diffusion has to be adjusted. I have to lower it down an order for my case.

Plus, the turning parameter in thin-film model (tffs) has to be lowered down from 5, suggested by the turtorial example, to 0.5.

Dear Mats Nigam and Mohammad Faizan I did solve the problem. As I said, the numerical diffusion has to be adjusted. I have to lower it down an order for my case. Plus, the turning parameter in thin-film model (tffs) has to be lowered down from 5, suggested by the turtorial example, to 0.5.
Shiuh-Hwa Shyu
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Posted: 6 years ago Oct 21, 2019, 9:09 p.m. EDT

I need to back off quite a bit. For the mixture model, I haven'r resolve the problem yet. I have read the wrong file, which is Bubbly Flow model.

I need to back off quite a bit. For the mixture model, I haven'r resolve the problem yet. I have read the wrong file, which is Bubbly Flow model.

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