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Problem with setting up two Continua

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Old   April 10, 2020, 22:46
Default Problem with setting up two Continua
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Yun Wang
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Hello, I am a new star CCM+ user and I need help with setting up with the continua.

I am trying to simulate gas flow in a T_junction valve. Two inlets and one outlet. I am trying to simulate two different type of gases mix in the valve (gas and Oxygen). I have extracted the internal volume of the valve and assigned it to region. However, I can not setup two continua (physics) to one region.

Can anyone please let me know what should I do?

Thank you
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Old   April 11, 2020, 06:18
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i suggest you do a tutorial related to such a case, and if you had been smart you would have done all the foundation tutorials first anyway before doing any real cases and would have found that the physics flow tutorial has similar physics to what you are wanting

if you have two continua your gases could not mix so revert to just one as a starting point
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Old   April 14, 2020, 04:56
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Lucky Tran
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One region can't have two physics. Split the regions and apply the different physics to each region, or rethink your approach. If you're just mixing two gases, I don't see why it needs two physics.
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Old   April 20, 2020, 11:36
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Hello and thank you very much for your previous reply. I have read the comments and tried to make some attempts to solve the problems. However, I still cannot get the simulation running. Therefore I would like to apologies in advance if my questions are too elementary.

I have tried to create a T-junction pipe with two Inlets and one Outlet: Inlet_1 one is Air and Inlet_2 is Oxygen, the mixture of gas is exiting on the outlet. I have extracted the internal volume as figure_1

Due to two type of gases were used in this study, I cannot assigned all the surface as one region as one of you pointed out in my previous post.

I have tried to assign the extracted volume as one region (Type: symmetry plane). The three inlet and outlet surfaces [inlet_1 (type: velocity inlet), Inlet_2 (velocity inlet) and Outlet (pressure outlet)] as three other regions.
I have created two physics models, One with Air property the other is Oxygen property. I have changed Region 3 (Inlet_2) physics continuum as Oxygen.
I can generate an automated volume mesh. However, when I hit the ‘run’ bottom to perform simulation, it gives out a warning saying ‘There is no volume mesh in region “Region 3). The mesh pipeline likely needs to be run first.’ And the simulation could not perform.

I have also tried to split the T-junction into two parts, show as Figure 2 and Figure 3


I was able to extract both parts internal volume. However, when I tried to generate volume mesh, it give a warning saying ‘surface mesh cannot generate on duplicate faces’. I was suspecting the connection surface between the two parts cannot share one ‘fill holes’ surface parts. I have generated two ‘fill holes’ parts for each body. However, the same warning message pop-up again and I cannot progress anymore.

Can anyone please let me know what have I done wrong and let me know the possible step to correct my errors?

Thank you very much for your attention, I am looking forward to your reply.
Attached Images
File Type: jpg Figure_1.jpg (21.4 KB, 6 views)
File Type: jpg Figure_2.jpg (12.7 KB, 6 views)
File Type: jpg Figure_3.jpg (13.3 KB, 6 views)
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Old   April 20, 2020, 12:09
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You can do this with one region, one physics if you use a multi-species model. I don't know why you make your own life hell by making it overly complicated.
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Old   April 21, 2020, 01:16
Default Problem with setting up two Continua
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i think you were sent in the wrong direction by luckytran's first reply to split regions. as I tried to tell you via educating yourself by doing relevant tutorials and now luckytran agrees you should have just one region and one physics continua. so get your regions back to one and ensure you have a good connected mesh right through the domain. then follow the the tutorial i suggested which is very similar to your physics requirement - is case you did not find it : Tutorials > Foundation Tutorials > Physics - Flow > Multi-Component Fluid: Steady Flow in a Dilution Pipe
ps you can of course have several regions for this type of analysis but they must be interfaced if you want flow between them and they must all use the same physics continuum

Last edited by ping; April 23, 2020 at 02:41.
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