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Old   July 24, 2002, 12:05
Default Multi-species question
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L Owens
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I have a novice question about Fluent's capabilities with calculating multiple species, single-phase flows. I've heard that the applicability is limited to species concentrations less than 0.8 or 0.9. Can that be true? Are surface tension effects considered?

Thanks for any info.
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Old   July 25, 2002, 03:32
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Laika
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species transport in no problem for Fluent.

Why would you have a species concentration of 0.95? In that case you let the main fluid be this species, and you track something with a concentration of 0.05.

Were do you encounter surface tension effects in a single-phase flow? There are only surface tension effects at the interface between two fluids. If you have such an interface, your flow is not single-phase.

Laika, still orbiting
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Old   July 25, 2002, 10:19
Default Re: Multi-species question
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L Owens
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For a given flow with multiple species I am imagining local regions of concentration that vary all over the map, with from 0 to 1 and everything in between. And by surface tension in single-phase flow, I'm thinking of something like oil-water type mixtures, where both are liquid phase, but surface tension surely drives the coalescing of oil pockets.

I know Fluent has a Volume-of-Fluid method and an Eulerian-Eulerian model and an Algebraic Slip Mixture Model, and I'm wondering if anyone can spell out the limitations on the various methods, i.e., why use VOF if you've got Eulerian-Eulerian? for processing time?
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Old   July 26, 2002, 03:35
Default Re: Multi-species question
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Laika
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Oil and water are immiscible. Therefore you cannot use species transport. Species transport simulations can't handle separation.

If you have a free surface to track, VOF is the only way.

If you're interested in small scale coalescing effects, you should go for eulerian-eulerian. Good results may require tuning and maybe sone UDF.

Laika, still orbiting
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