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Outflow BC - Concentration gradient

Posted 29.05.2013, 05:43 GMT-4 1 Reply

Francesca Messina
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Dear all,

I am using the Transport of Diluted Species physics.

Until now I have always used "outflow" as outlet boundary condition. This means that the gradient of the concentration, at the outlet section, is zero.

Someone knows if is it possible to set, at the outlet section, the same concentration gradient that there is at the nearest mesh nodes (instead of zero)?

Thank you very much.

Best Regards,

Francesca Messina
1 Reply Last Post 29.05.2013, 11:09 GMT-4
Niklas Rom COMSOL Employee

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Posted: 1 decade ago 29.05.2013, 11:09 GMT-4
Hi Francesca, the question is if this is well posed. The Outflow condition in mass transfer physics can be interpreted as "nothing happens downstream". That is, no concentration changes happen downstream. If something happens downstream, you may instead want to extend the computational domain so that it captures those phenomena.

Just a hunch.


Dear all,

I am using the Transport of Diluted Species physics.

Until now I have always used "outflow" as outlet boundary condition. This means that the gradient of the concentration, at the outlet section, is zero.

Someone knows if is it possible to set, at the outlet section, the same concentration gradient that there is at the nearest mesh nodes (instead of zero)?

Thank you very much.

Best Regards,

Francesca Messina


Hi Francesca, the question is if this is well posed. The Outflow condition in mass transfer physics can be interpreted as "nothing happens downstream". That is, no concentration changes happen downstream. If something happens downstream, you may instead want to extend the computational domain so that it captures those phenomena. Just a hunch. [QUOTE] Dear all, I am using the Transport of Diluted Species physics. Until now I have always used "outflow" as outlet boundary condition. This means that the gradient of the concentration, at the outlet section, is zero. Someone knows if is it possible to set, at the outlet section, the same concentration gradient that there is at the nearest mesh nodes (instead of zero)? Thank you very much. Best Regards, Francesca Messina [/QUOTE]

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