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Old   February 18, 2009, 21:54
Default *** Species generation rate? ***
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I am modelling humidity generated by a human in an air volume. I use the species transport model together with heat transfer.

My question is: How do you change the boundary condition for any species from "constant mass fraction" to a generation rate, i.e. mass fraction of h2o per second?

For heat transfer you can specify heat generation rates in Watts so why not a moisture generation rate instead of a constant value?

I have found how to add source terms for moisture but this is just for a fluid zone and has no effect on choices in the boundary conditions. Can anybody help please?

Many thanks,

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Old   February 21, 2009, 21:58
Default *** The Solution ***
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I spoke to Fluent about this. There is no functionality to set a species flux on boundaries.

The way to get around it is to create a small volume next to the boundary where you want a species flux. This can be done in gambit before mesh export or you can go adapt->mark to mark a face, then grid-separate to separate a volume one-cell away from the surface. Then print the volume of this, then you can work out the flux.

Then in go to that volume in the boundary condition panel, click set, then add a source term for species and mass. You can then set the appropriate flux in Kg/m^2*s.

Also, the reference temp is 288.15 so if your species is at a different temp to this, must add an energy source term too with a value of the Species flux * Cp * (T-288.15), where T = species temp.

I hope this helps somebody in the future.

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