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mass sink as a function of concentration

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Old   May 7, 2010, 02:19
Default mass sink as a function of concentration
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ranjith
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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...

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Old   May 7, 2010, 07:39
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Glenn Horrocks
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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.
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Old   May 7, 2010, 23:50
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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
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Old   May 8, 2010, 06:46
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Glenn Horrocks
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I thought so. But don't you want a volumetric source, not a boundary source?
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Old   May 9, 2010, 23:26
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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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