bubble rising problem

swamysrikanth · September 9, 2010, 08:55

hello frnds,
can anyone explain the way to mesh for bubble rising in a column. i want to study the dynamics of the bubble and deformation of bubble with time. i am confused with the part of creation of bubble...whether i have to create a bubble geometry or i can initialize the bubble injection through boundary conditions. how to do the meshing at critical path of bubble rising through the column...

thanks in advance
srikanth

PSYMN · September 21, 2010, 17:38

There are phase change models that will predict bubbling along the walls (such as in a nuclear reactor).

But it sounds to me that you want to do a bubble of a known diameter rising thru a column...

Do you need to have motion relative to the column (are the ends of the column important) or can we just pretend the bubble is kept still by flow moving the other way? (much simpler to model)

Does the bubble stay in the middle of the column? I hope so.

If you wanted to try that, then you would be talking a nice Hexa mesh with an ogrid around and thru he bubble. It can be meshed in a few minutes, half an hour if you want to get picky about the edge distributions.

If you have deformation, you would have an FSI situation where the flow creates pressures which cause the bubble to deform, which changes the flow and resulting pressures, etc...

I recommend trying a simpler study first (a rigid sphere transient flow analysis), then move towards setting up an FSI solution.

I think you will find this to be quite challenging (mixture of transient and FSI). Have you found any whitepapers on this?

You may also ask this question on the Fluent solver boards in case there is some simpler way to model this two phase problem (not using FSI).

swamysrikanth · September 22, 2010, 09:00

thanks for ur reply,
i constructed a hexa mesh on overall column. my case is bubble is moving and it is located in the centre of the column. and it is also deforming with time. and i am running the simulation using vof model.

yesenia · May 31, 2016, 12:09

Hi srikanth!

I'm also trying to simulate a bubble motion in fluent using VOF. I just want to know how big was your geometry and how do you mesh it.
I have a geometry of 18x18x18 mm and the bubble is 2mm. But I want to have a refine mesh in the bubble and interface. I would like to have cell with 2.5 microns in the interface but I'm not sure what is the best way to do without having a huge amount of elements.

Thanks

September 9, 2010, 08:55	bubble rising problem	#1
swamysrikanth New Member srikanth Join Date: Nov 2009 Posts: 22 Rep Power: 17	hello frnds, can anyone explain the way to mesh for bubble rising in a column. i want to study the dynamics of the bubble and deformation of bubble with time. i am confused with the part of creation of bubble...whether i have to create a bubble geometry or i can initialize the bubble injection through boundary conditions. how to do the meshing at critical path of bubble rising through the column... thanks in advance srikanth

September 21, 2010, 17:38	Fluid Structure Interaction (even if the structure is just bubble surface tension)	#2
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	There are phase change models that will predict bubbling along the walls (such as in a nuclear reactor). But it sounds to me that you want to do a bubble of a known diameter rising thru a column... Do you need to have motion relative to the column (are the ends of the column important) or can we just pretend the bubble is kept still by flow moving the other way? (much simpler to model) Does the bubble stay in the middle of the column? I hope so. If you wanted to try that, then you would be talking a nice Hexa mesh with an ogrid around and thru he bubble. It can be meshed in a few minutes, half an hour if you want to get picky about the edge distributions. If you have deformation, you would have an FSI situation where the flow creates pressures which cause the bubble to deform, which changes the flow and resulting pressures, etc... I recommend trying a simpler study first (a rigid sphere transient flow analysis), then move towards setting up an FSI solution. I think you will find this to be quite challenging (mixture of transient and FSI). Have you found any whitepapers on this? You may also ask this question on the Fluent solver boards in case there is some simpler way to model this two phase problem (not using FSI).

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September 22, 2010, 09:00		#3
swamysrikanth New Member srikanth Join Date: Nov 2009 Posts: 22 Rep Power: 17	thanks for ur reply, i constructed a hexa mesh on overall column. my case is bubble is moving and it is located in the centre of the column. and it is also deforming with time. and i am running the simulation using vof model.

May 31, 2016, 12:09		#4
yesenia New Member yesenia Join Date: May 2015 Location: sydney Posts: 4 Rep Power: 11	Hi srikanth! I'm also trying to simulate a bubble motion in fluent using VOF. I just want to know how big was your geometry and how do you mesh it. I have a geometry of 18x18x18 mm and the bubble is 2mm. But I want to have a refine mesh in the bubble and interface. I would like to have cell with 2.5 microns in the interface but I'm not sure what is the best way to do without having a huge amount of elements. Thanks