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flo777 February 27, 2010 12:34

mixing of 2 different fluids
I want to know how to mix 2 different fluids. I have enabled the beta options for multi-domains, but then when I create the 2 domains, I can only select the assembly as the location. The error I am getting is that the same boundary has been assigned to more than one domain.
Can anyone tell me how to get over this problem?

ghorrocks February 28, 2010 18:53

What do you mean by "mix 2 fluids"? CFX has dozens of models to handle different regimes of mixing. Free surface models, Eularian models, particle tracking, additional variables, fluidised bed models etc etc. Until you explain what you are doing we can't help.

flo777 February 28, 2010 20:15

I am new to CFX, don't know of what it is capable, but what I am trying to do is show the mixing between air and octane gas at specified velocities.

The boundaries on the geometry I have created has 2 inlets and 1 outlet. I thought it's as easy as enabling the beta features, and creating 2 different domains for each inlet, but then the domain location interferes and I don't know how to deal with that. I also don't know how to deal with the outlet, which is a mixture of air and octane.


ghorrocks February 28, 2010 20:22

You don't define different domains for each component. It is one domain with a multi component mixture.

Have a look in the tutorial examples. There are plenty of examples of how to do multi component mixtures.

flo777 February 28, 2010 20:37

Thanks for quick reply.

I heard that CFX also has break-up models? I would also like to model liquid octane injection, and see the mixture between the air and the spray.

Could I do this with a single domain and multiple component mixture? Do you know if there are tutorials on break-up models?


ghorrocks February 28, 2010 21:04

Yes, CFX has breakup models. They were developed for fuel injection for SI and CI engines and if you are using liquid octane they may be useful.

But make sure you know what you are talking about. Mixtures of gasses can be modelled with multicomponent mixtures. Breakup of liquid sprays is now a multiphase thing as you have liquid and gaseous phases. Multiphase and multicomponent are totally different. And yes, you can have both a multiphase AND multicomponent models where the gas phase is a mixture of gasses. These are complicated models and not for the feint hearted.

flo777 March 8, 2010 23:40

break-up model
Do you know where I could get a tutorial explaining the break-up model?
I just want to get started with this, so the very basic, if there is something like that.. as I mentioned before, I want to model a certain mass flow of liquid octane, injected at a certain pressure

ghorrocks March 9, 2010 05:27

You will have to contact CFX support to get an example.

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