Outlet BC for granular two-phase flow

Rubblevg · March 13, 2017, 10:47

Hi all,

I am trying to model a granular two-phase flow where only the liquid phase can leave the domain. In reality a filter is placed in front of the outlet to keep the particles from leaving the domain, but since I don't know the properties of this filter I cannot really use a porous zone condition. Therefore, I thought about modelling the outlet in a different way. If I program a boundary that behaves as an ordinary pressure outlet for the liquid phase and a wall for the particle phase, my problem should be solved.

However, I am not sure where to start. I am fairly new to UDFs, but to me it seems that only the existing boundary conditions of FLUENT can be modified using UDFs. For example gauge pressure and inlet velocity profiles can be given by a UDF. Are there also other methods of modifying boundary conditions so that only liquid can leave the domain?

I hope you can help me out!

Rubblevg · March 17, 2017, 06:11

Update: One solution I found to solve my problem is by creating an additional body in front of the outlet. Then, when selecting the body at 'cell zone conditions' it is possible to set fixed values for a specific phase. If all velocity components of the granular phase are set zero, the problem is in principle solved.

One disadvantage however is that is seems to have a negative effect on the convergence. So, if anyone has an alternative solution I would like to hear it!

March 13, 2017, 10:47	Outlet BC for granular two-phase flow	#1
Rubblevg New Member Ruben Join Date: Feb 2017 Location: Eindhoven Posts: 22 Rep Power: 9	Hi all, I am trying to model a granular two-phase flow where only the liquid phase can leave the domain. In reality a filter is placed in front of the outlet to keep the particles from leaving the domain, but since I don't know the properties of this filter I cannot really use a porous zone condition. Therefore, I thought about modelling the outlet in a different way. If I program a boundary that behaves as an ordinary pressure outlet for the liquid phase and a wall for the particle phase, my problem should be solved. However, I am not sure where to start. I am fairly new to UDFs, but to me it seems that only the existing boundary conditions of FLUENT can be modified using UDFs. For example gauge pressure and inlet velocity profiles can be given by a UDF. Are there also other methods of modifying boundary conditions so that only liquid can leave the domain? I hope you can help me out!

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March 17, 2017, 06:11		#2
Rubblevg New Member Ruben Join Date: Feb 2017 Location: Eindhoven Posts: 22 Rep Power: 9	Update: One solution I found to solve my problem is by creating an additional body in front of the outlet. Then, when selecting the body at 'cell zone conditions' it is possible to set fixed values for a specific phase. If all velocity components of the granular phase are set zero, the problem is in principle solved. One disadvantage however is that is seems to have a negative effect on the convergence. So, if anyone has an alternative solution I would like to hear it!