[HHOS]

Hello,

I am trying to simulate the drying so to say of a domain with Fluent.


As starting condition, I have a domain with water at a 80% Relative humidity. One side is open to the surrounding as a pressure inlet with defined water mass fraction. From another side I want to extract water from the air. Only water. Think of something that sucks water in. That way, the volume of water vapor extracted should be replaced on the other side by air-vapor mixture.


See attached image for the sketch I did.



I have been trying to come up with ideas. Using UDFs, negative sources (sink) to extract water. But nothing worked as I wanted.


So, how to have a boundary to extract a single species from the mixture??


Thanks in advance.

[LuckyTran]

The problem is you want to only extract water but your working fluid is wet air, which is not water.

It is straightforward if you just use species mass transport equations and have individual transport equations for air and water. But there is no free lunch because now you have to calculate relative humidity from mass fractions.

[HHOS]

Oh my, LuckyTran, Straightforward?


It is kind of embarrassing to ask this question, because I feel I should know it, but, how do I do that? I mean, in the models I have tried, the mixture is treated as a single fluid.


When I use Eulerian multiphase, the transport equations are solved for each phase separately, but I don't know how to make the same happen to track each species separately -and hence have the possibility to have a massflow outlet with the single species-.


Should I just use User Defined Scalars?? Is that the approach you are talking about?


The problem seems simple enough that Fluent would have such a thing already embedded, without using UDS.


I really look forward to a reply.


Thank you!


Regards.