Mass Transfer UDF using Fluent VOF

Anirudh_Deodhar · February 7, 2011, 16:21

Hello, I am studying the air bubble dynamics from a submerged orifice in pool of aqueous soln of surfactants. As surfactant molecules adsorb and desorb on the moving bubble interface, I need to put a concentration boundary condn on the moving interface. (need to specify a specific concentration function on the bubble interface). As I am using VOF module in Fluent 12, my question is, can I specify a concentration BC on the moving bubble interface? How do I limit my concetration BC equation to region where volume fraction is between 0 to 1? Can I write a UDF for the same?

ComputerGuy · February 9, 2011, 22:43

If your interface is actually defined by the fluid flow (it's arbitrarily deformable), you'll need to write a udf which loops over cells, determines the interface (C_VOF !=0 && C_VOF!=1), and then sets the mass fraction of the surfactants at the interface. While it's a phase interface, it's not really a boundary condition in the Fluent sense.

ComputerGuy

Anirudh_Deodhar · February 14, 2011, 16:07

@Computer Guy

Thank you very much for your reply.
I am still working on it. I might have more questions for you later. :P

But thank you very much for your prompt reply.

~
Anirudh

Tensian · November 18, 2015, 10:29

Hi,

This seems to be an old thread, but I will try anyway...

I am also working in my UDF to define mass transfer between 2phases. I need a transitory mass transfer, it is to said, the mass transfer between phases varies with time.

I know how to define a mass transfer in this sense. The question is I am not sure if the value I am sending to the mass transfer is correct. I have available a curve that measures concentration of a substance (ppm) with time, so, for example, at t=1 I have 24ppm of phase 2, at t=2 I get 20 ppm of phase 2 and so on.

I guess if I impose directly this values (fitted in a time-dependent curve) in my UDF I will be doing it wrong. I fairly remember I have read somewhere that you are specifying kg/m3/s.

Could any UDF expert seed some light on this issue?

Thank you in advance.

Regards,

Tensi

February 7, 2011, 16:21	Mass Transfer UDF using Fluent VOF	#1
Anirudh_Deodhar New Member Andeo Join Date: Jun 2010 Location: Pune, India Posts: 12 Rep Power: 16	Hello, I am studying the air bubble dynamics from a submerged orifice in pool of aqueous soln of surfactants. As surfactant molecules adsorb and desorb on the moving bubble interface, I need to put a concentration boundary condn on the moving interface. (need to specify a specific concentration function on the bubble interface). As I am using VOF module in Fluent 12, my question is, can I specify a concentration BC on the moving bubble interface? How do I limit my concetration BC equation to region where volume fraction is between 0 to 1? Can I write a UDF for the same?

February 14, 2011, 16:07	Reply	#3
Anirudh_Deodhar New Member Andeo Join Date: Jun 2010 Location: Pune, India Posts: 12 Rep Power: 16	@Computer Guy Thank you very much for your reply. I am still working on it. I might have more questions for you later. :P But thank you very much for your prompt reply. ~ Anirudh

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February 9, 2011, 22:43		#2
ComputerGuy Senior Member Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 16	If your interface is actually defined by the fluid flow (it's arbitrarily deformable), you'll need to write a udf which loops over cells, determines the interface (C_VOF !=0 && C_VOF!=1), and then sets the mass fraction of the surfactants at the interface. While it's a phase interface, it's not really a boundary condition in the Fluent sense. ComputerGuy

November 18, 2015, 10:29		#4
Tensian Senior Member James Join Date: May 2013 Posts: 116 Rep Power: 13	Hi, This seems to be an old thread, but I will try anyway... I am also working in my UDF to define mass transfer between 2phases. I need a transitory mass transfer, it is to said, the mass transfer between phases varies with time. I know how to define a mass transfer in this sense. The question is I am not sure if the value I am sending to the mass transfer is correct. I have available a curve that measures concentration of a substance (ppm) with time, so, for example, at t=1 I have 24ppm of phase 2, at t=2 I get 20 ppm of phase 2 and so on. I guess if I impose directly this values (fitted in a time-dependent curve) in my UDF I will be doing it wrong. I fairly remember I have read somewhere that you are specifying kg/m3/s. Could any UDF expert seed some light on this issue? Thank you in advance. Regards, Tensi