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Multi-fluid and multi-phase modeling

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Old   December 15, 2009, 04:20
Default Multi-fluid and multi-phase modeling
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anonymous
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Is it possible to model a system consisting of more than one fluid and use a multiphase model in the same time?

Everytime i activate the multiphase models, a primary phase has to be defined and it exists in all the fluid sections. How can i get around that?

one section of the system has a velocity-inlet/oulet and the other section consists of walls shaped as a pipe that loops. Each section contains a completely different fluid.

please enlighten me,

Thank you
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Old   December 15, 2009, 10:57
Default different fluid in domains
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Hi,
Multiple fluids existing in the system is the basic essence of MP flows. For different regions working with different fluids, try patching the regions initially with different fluid fractions and make sure the bc for each section has vf = 1 for fluid that needs to be circulated and other fluid 0. For multiphase cases, there has to be a primary and secondary phase to define interactions. This is how mp cases are set up numerically.


/CFDtoy

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Originally Posted by CFDUSER-A View Post
Is it possible to model a system consisting of more than one fluid and use a multiphase model in the same time?

Everytime i activate the multiphase models, a primary phase has to be defined and it exists in all the fluid sections. How can i get around that?

one section of the system has a velocity-inlet/oulet and the other section consists of walls shaped as a pipe that loops. Each section contains a completely different fluid.

please enlighten me,

Thank you
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Old   December 16, 2009, 14:40
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Thank you for the reply, i tried the exact thing you wrote earlier but my system diverges rapidly. Once i patch the fluid domain problems start and the iterations stop converging. Do you have any suggestions on what to do once that occurs.

Thanks,
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Old   December 16, 2009, 15:00
Default runs
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Solution convergence/divergence is based on your set up. For example, you could have patched a domain with fluid "a" but at the boundaries may have insisted on having 0 fraction of a => there is fluid b = 1-a entering a domain filled with 'a' and then problem becomes more of adjusting your solver controls.

Make sure there is good inflow and outflow conditions specified.

I would say just be very careful with your boundary conditions for these systems where you patch..do not let fluid a and b mix rapidly ..i.e. adjust time step / courant number those kind of things i would pay attention once the system has been set up well.

/CFDtoy

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Originally Posted by CFDUSER-A View Post
Thank you for the reply, i tried the exact thing you wrote earlier but my system diverges rapidly. Once i patch the fluid domain problems start and the iterations stop converging. Do you have any suggestions on what to do once that occurs.

Thanks,
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