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-   -   mass sink as a function of concentration (http://www.cfd-online.com/Forums/cfx/75851-mass-sink-function-concentration.html)

 ranjith May 7, 2010 02:19

mass sink as a function of concentration

Hi,
I am simulating flow and oxygen consumption by cells in a bioreactor. My fluid is water with oxygen dissolved in it. I am modelling the cells as a mass sink for oxygen. The problem is that the amount of mass consumed by the cells is a function of the oxygen concentration in the vicinity of the cells .When I look at CFX I can only specify constant flux rates for a boundary sink. Please advice on how I can model the sink as a function of the oxygen concentration. Would it be better if I introduce an additional variable...

Ranjith

 ghorrocks May 7, 2010 07:39

Isn't it a volume mass fraction sink, not a boundary sink? I am not sure what restrictions volume sinks have but I think you will be able to make it a function of the local mass fraction. Not sure, just try it. If not then your suggestion of using an additional variable might be a good work around. What this will probably do is to make the additional variable lag the mass fraction by an iteration which may improve numeric stability.

 ranjith May 7, 2010 23:50

Thanks Glenn for your reply. I have infact completed the simulation. CFX does take expressions for boundary sources as a function of local mass fraction.

Thank you
Ranjith

 ghorrocks May 8, 2010 06:46

I thought so. But don't you want a volumetric source, not a boundary source?

 ranjith May 9, 2010 23:26

True, it is a volumetric sink. But I just converted it into a boundary sink...I just took the the volume function multiplied it by the volume of the cells and then divided it by the area.... I hope that is ok...:)

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