Two different fluids in CFX, possible?

Knowledge · November 24, 2020, 15:56

Hi

I defined my own material in CFX for one of my fluid domains. However, when I apply this material for one of the domains it automatically also apply for the other fluid domain. I want the other fluid domain to be air.
What can I do? Can CFX not handle this problem? Is it fine to define the fluid domain as solid and give it the same thermal properties as air?

thanks!

Opaque · November 24, 2020, 16:43

Can you explain what you are trying to model?

ghorrocks · November 24, 2020, 16:48

CFX cannot handle (by default) fluid domains with different fluids in them.

Also, in fluid domains CFX solves the Navier Stokes equations (and any additional equations you have added). In solid domains it just solves the heat equation by default. So if all you want in a domain is the heat equation then call it a solid domain.

Gert-Jan · November 24, 2020, 18:46

Go to Edt -> Options and look for Enable Beta Features and Enforce Constant Physics.

If you untick the last one, then you can define different volumes with different materials like air and water for e.g. a air-water heat exchanger.

November 24, 2020, 15:56	Two different fluids in CFX, possible?	#1
Knowledge Member Sara Join Date: Nov 2020 Posts: 44 Rep Power: 5	Hi I defined my own material in CFX for one of my fluid domains. However, when I apply this material for one of the domains it automatically also apply for the other fluid domain. I want the other fluid domain to be air. What can I do? Can CFX not handle this problem? Is it fine to define the fluid domain as solid and give it the same thermal properties as air? thanks!

November 24, 2020, 16:43		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,811 Rep Power: 32	Can you explain what you are trying to model? __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

November 24, 2020, 16:48		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,715 Rep Power: 143	CFX cannot handle (by default) fluid domains with different fluids in them. Also, in fluid domains CFX solves the Navier Stokes equations (and any additional equations you have added). In solid domains it just solves the heat equation by default. So if all you want in a domain is the heat equation then call it a solid domain. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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November 24, 2020, 18:46		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,834 Rep Power: 27	Go to Edt -> Options and look for Enable Beta Features and Enforce Constant Physics. If you untick the last one, then you can define different volumes with different materials like air and water for e.g. a air-water heat exchanger.