Fluid must entrain fluid but doesn't

CneSpaulding · June 23, 2014, 04:51

Hi,

This is natural convection.
I'm trying to simulate a quarter of air bubble (not rising) under water.
Under my bubble there is an heat flux. I used the Boussinesq model in the air and water,
and because the velocity in my bubble is 3 times more than in the water I think that the air must entrain the water in the same direction near the interface but it doesn't...

I used, for my interface, Baffle//slip//Conducting

For the general models it's:

Boussinesq, steady, coupled flow/Energy, Gravity

Thanks for reading

me3840 · June 23, 2014, 16:00

Why would the air impart any momentum through a baffle interface that's slipping?

CneSpaulding · June 24, 2014, 06:47

I know that a Baffle interface is a wall, that's why air doesn't entrain the water,
my question is: How do I do to create an interface that is not a wall and respect velocity throught the interface and thermal comportment?!

me3840 · June 25, 2014, 06:27

You need to make the interface an internal interface for that.

But that would allow the bubble to rise, which you state you don't want. I'm not sure what physical conditions would case that.

I assumed you're using the VOF method.

June 23, 2014, 04:51	Fluid must entrain fluid but doesn't	#1
CneSpaulding New Member Victor Pannel Join Date: Mar 2014 Location: Marseille (France) Posts: 12 Rep Power: 12	Hi, This is natural convection. I'm trying to simulate a quarter of air bubble (not rising) under water. Under my bubble there is an heat flux. I used the Boussinesq model in the air and water, and because the velocity in my bubble is 3 times more than in the water I think that the air must entrain the water in the same direction near the interface but it doesn't... I used, for my interface, Baffle//slip//Conducting For the general models it's: Boussinesq, steady, coupled flow/Energy, Gravity Thanks for reading

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June 23, 2014, 16:00		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Why would the air impart any momentum through a baffle interface that's slipping?

June 24, 2014, 06:47		#3
CneSpaulding New Member Victor Pannel Join Date: Mar 2014 Location: Marseille (France) Posts: 12 Rep Power: 12	I know that a Baffle interface is a wall, that's why air doesn't entrain the water, my question is: How do I do to create an interface that is not a wall and respect velocity throught the interface and thermal comportment?!

June 25, 2014, 06:27		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	You need to make the interface an internal interface for that. But that would allow the bubble to rise, which you state you don't want. I'm not sure what physical conditions would case that. I assumed you're using the VOF method.