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Eulerian phase gas diameter

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Old   July 29, 2015, 20:43
Default Eulerian phase gas diameter
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Why does Fluent need a particle diameter for a gaseous Eulerian phase. If it does not require one for air if air is primary phase, why is a particle diameter needed if I have air or any other gas as the secondary phase.
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Old   July 30, 2015, 02:44
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The primary phase is the continuous phase - it doesn't need a diameter because it is a continuum.

The secondary phase is a discrete phase - it consists of non-connected particulate entities, whether these are droplets, bubbles or particles - these entities have a certain diameter. This diameter needs to be supplied to calculate interphase forces, such as drag.

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Old   July 30, 2015, 02:57
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So, if the secondary phase was water vapor, how do i know what the diameter is. Should i just randomly put on a very very small diameter for a 'gas type' secondary phase?

Thanks
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Old   August 14, 2015, 05:59
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hwet,
it depends on your problem.

if you're modelling gas bubbles in a liquid, then the vapour is the secondary phase.
if you're modelling say, steam condensation, then the liquid is the secondary phase, because you have droplets of liquid suspended in a gas.
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