The problem in modeling the oxygen concentration is flow water

zhixin · December 17, 2015, 09:51

Hi, everyone.
I been working on the concentration of oxygen in flow water contained in a elbow pipe. And I use the species transport and k-e turbulence model.
I assume the inlet is velocity-inlet, and assume the oxygen concentration is saturated(4.84e-06)
The questions is when I finished the computation and check the contours of mass concentration of O2 in wall and int_fluid. It seems like the oxygen concentration didn't change at all.

At first I thought when the water flow through the elbow. The pressure's change and the turbulence will lead to the diffidence of oxygen distribution. So anyone can tell me if I was wrong during the modeling process or the results is right.

Thanks a lot.

CeesH · December 18, 2015, 06:16

Hi,

If you are feeding a saturated oxygen solution, why would the oxygen concentration change? As long as there is no consumption, there doesn't seem to be a reason why it should. What are the physics related to oxygen transport and consumption/production in your model?

Best,
Cees

zhixin · December 18, 2015, 07:45

Quote:

Originally Posted by CeesH

Hi,

If you are feeding a saturated oxygen solution, why would the oxygen concentration change? As long as there is no consumption, there doesn't seem to be a reason why it should. What are the physics related to oxygen transport and consumption/production in your model?

Best,
Cees

Thank for your reply.
I read a paper about modeling the corrosion in the pipe(use the oxygen diffusion to express the corrosion degree and the oxygen is consumed totally at the wall boundary by reacting with metal iron such as Fe).
Your reply reminds me to set the oxygen concentration at wall to be zero. But I don't know if it works.

CeesH · December 18, 2015, 08:13

Hi,
I have no experience in that field, but it seems to me you will need to set some reactive boundary condition or so; check the wall boundary conditions for species and the surface reaction model. You will at least need to specify some physical model by which oxygen can leave the domain, either via consumption or by transport through the wall. Lacking such a model, your oxygen will only move, but as the concentration everywhere is equal there will be no gradients whatsoever.

zhixin · December 18, 2015, 08:19

Hi Cees,
I'll try it later. Thanks

December 17, 2015, 09:51	The problem in modeling the oxygen concentration is flow water	#1
zhixin Member 志新高(Zhixin Gao) Join Date: Aug 2014 Location: hz.China Posts: 30 Rep Power: 12	Hi, everyone. I been working on the concentration of oxygen in flow water contained in a elbow pipe. And I use the species transport and k-e turbulence model. I assume the inlet is velocity-inlet, and assume the oxygen concentration is saturated(4.84e-06) The questions is when I finished the computation and check the contours of mass concentration of O2 in wall and int_fluid. It seems like the oxygen concentration didn't change at all. At first I thought when the water flow through the elbow. The pressure's change and the turbulence will lead to the diffidence of oxygen distribution. So anyone can tell me if I was wrong during the modeling process or the results is right. Thanks a lot.

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December 18, 2015, 06:16		#2
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Hi, If you are feeding a saturated oxygen solution, why would the oxygen concentration change? As long as there is no consumption, there doesn't seem to be a reason why it should. What are the physics related to oxygen transport and consumption/production in your model? Best, Cees

December 18, 2015, 08:13		#4
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Hi, I have no experience in that field, but it seems to me you will need to set some reactive boundary condition or so; check the wall boundary conditions for species and the surface reaction model. You will at least need to specify some physical model by which oxygen can leave the domain, either via consumption or by transport through the wall. Lacking such a model, your oxygen will only move, but as the concentration everywhere is equal there will be no gradients whatsoever.

December 18, 2015, 08:19		#5
zhixin Member 志新高(Zhixin Gao) Join Date: Aug 2014 Location: hz.China Posts: 30 Rep Power: 12	Hi Cees, I'll try it later. Thanks