Eulerian phase gas diameter

hwet · July 29, 2015, 21:43

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.

CeesH · July 30, 2015, 03:44

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.

Best,
Cees

hwet · July 30, 2015, 03:57

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

CFDYourself · August 14, 2015, 06:59

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.

July 29, 2015, 21:43	Eulerian phase gas diameter	#1
hwet Senior Member Join Date: Mar 2014 Posts: 375 Rep Power: 13	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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July 30, 2015, 03:44		#2
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	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. Best, Cees

July 30, 2015, 03:57		#3
hwet Senior Member Join Date: Mar 2014 Posts: 375 Rep Power: 13	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

August 14, 2015, 06:59		#4
CFDYourself Member Jim Join Date: May 2015 Posts: 47 Rep Power: 11	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.