Simulation of droplet formation in a T-Junction

Sumith · April 4, 2016, 01:32

Hello,

I am trying to simulate a segmented flow(Bubble formation) in a T-Junction channel where the two fluids are water and oil(2 inlets and 1 outlet). water is the primary phase and oil is the secondary phase. i am using Ansys Fluent student version but am unable to get the simulation.

Its been very long and i think am going wrong somewhere in Patching or initialising. i am confused in defining volume fraction and Mixture velocity.

Can anybody help me with complete steps, it will be a great help.

regards

CeesH · April 4, 2016, 04:52

Can you specify a bit more what you are doing?
What multiphase model are you using?

Sumith · April 4, 2016, 09:20

Thanks for your reply.

My Geometry is a Cross section with three Inlets and one outlet. Water Flows in Inlet one, Oil in Inlet two and three.
I am using VOF Model. I have defined Materials, Water as my Primary Phase and Oil as Secondary. The Properties like Density and Viscosity are defined for Water and oil. The surface tension has been set in the 'Phase Interaction'.

When it Comes to Boundary Conditions for Inlet 1, I can select three phases, Water, oil and Mixture. When I select 'Water' as my phase and 'Velocity-Inlet' as my type, I am not able to edit any Parameters. I am getting this message 'This page is not applicable under current settings'. When I select 'Mixture' as my phase, I can define 'Mixture Velocity' but I don't think it's a Correct BC since the phase is 'Mixture' in stead of 'Water'.
Kindly help me with this.

Thank You

CeesH · April 4, 2016, 10:46

For the VOF model, both phases share the momentum equation - hence there is no distinction between water and oil in terms of velocity, the mixture velocity applies for both phases at any location. This is allowed since at we assume that (except for the interface cells) a gridcell contains either water or oil, not both, and at the interface there is no slip between the phases. So, you indeed only need to set the mixture velocity at the entrance. The volume fraction then determines what exactly is flowing in.

Sumith · April 5, 2016, 00:25

I Really Appreciate your help. Can You Tell Me how to Patch the Volume fraction for Oil after Running the calculation.
I believe I am going wrong over there too. What 'Region' I Have to Adapt for 'Patching' and How to Manipulate the Volume Fraction so that I get a Segmented flow?

Thank You in Advance

hariswch2 · April 5, 2016, 01:31

Quote:

Originally Posted by Sumith

I Really Appreciate your help. Can You Tell Me how to Patch the Volume fraction for Oil after Running the calculation.
I believe I am going wrong over there too. What 'Region' I Have to Adapt for 'Patching' and How to Manipulate the Volume Fraction so that I get a Segmented flow?

Thank You in Advance

Same kind of work on microfluidics, I did in my PG....pls refer my published journal, below is the link (http://link.springer.com/article/10....206-014-9103-1)

Hope it may clear all your doubts...
Let me know If you want any help..

CeesH · April 5, 2016, 03:14

If I am correct, your problem involves the formation of droplets in flow-focusing, right? So what I think you need to do is simply set the volume fraction of you water face to 1 for the water outlet, and 0 to the others (under boundary condition > phase 2 > multiphase)

No patching is required for that problem. But maybe I am wrong in what your goal is, please let me know if that is the case.

April 4, 2016, 01:32	Simulation of droplet formation in a T-Junction	#1
Sumith New Member Sumith jain Join Date: Apr 2016 Posts: 3 Rep Power: 10	Hello, I am trying to simulate a segmented flow(Bubble formation) in a T-Junction channel where the two fluids are water and oil(2 inlets and 1 outlet). water is the primary phase and oil is the secondary phase. i am using Ansys Fluent student version but am unable to get the simulation. Its been very long and i think am going wrong somewhere in Patching or initialising. i am confused in defining volume fraction and Mixture velocity. Can anybody help me with complete steps, it will be a great help. regards

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April 4, 2016, 04:52		#2
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Can you specify a bit more what you are doing? What multiphase model are you using?

April 4, 2016, 09:20		#3
Sumith New Member Sumith jain Join Date: Apr 2016 Posts: 3 Rep Power: 10	Thanks for your reply. My Geometry is a Cross section with three Inlets and one outlet. Water Flows in Inlet one, Oil in Inlet two and three. I am using VOF Model. I have defined Materials, Water as my Primary Phase and Oil as Secondary. The Properties like Density and Viscosity are defined for Water and oil. The surface tension has been set in the 'Phase Interaction'. When it Comes to Boundary Conditions for Inlet 1, I can select three phases, Water, oil and Mixture. When I select 'Water' as my phase and 'Velocity-Inlet' as my type, I am not able to edit any Parameters. I am getting this message 'This page is not applicable under current settings'. When I select 'Mixture' as my phase, I can define 'Mixture Velocity' but I don't think it's a Correct BC since the phase is 'Mixture' in stead of 'Water'. Kindly help me with this. Thank You

April 4, 2016, 10:46		#4
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	For the VOF model, both phases share the momentum equation - hence there is no distinction between water and oil in terms of velocity, the mixture velocity applies for both phases at any location. This is allowed since at we assume that (except for the interface cells) a gridcell contains either water or oil, not both, and at the interface there is no slip between the phases. So, you indeed only need to set the mixture velocity at the entrance. The volume fraction then determines what exactly is flowing in.

April 5, 2016, 00:25		#5
Sumith New Member Sumith jain Join Date: Apr 2016 Posts: 3 Rep Power: 10	I Really Appreciate your help. Can You Tell Me how to Patch the Volume fraction for Oil after Running the calculation. I believe I am going wrong over there too. What 'Region' I Have to Adapt for 'Patching' and How to Manipulate the Volume Fraction so that I get a Segmented flow? Thank You in Advance

April 5, 2016, 03:14		#7
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	If I am correct, your problem involves the formation of droplets in flow-focusing, right? So what I think you need to do is simply set the volume fraction of you water face to 1 for the water outlet, and 0 to the others (under boundary condition > phase 2 > multiphase) No patching is required for that problem. But maybe I am wrong in what your goal is, please let me know if that is the case.