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Old   July 25, 2005, 05:07
Default transport & diffusion sc. boundaries
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some of you may have already read some similar messages, I have been trying to do this for quite some time and still trying to look if somebody out there could give me a hand.

Suppose you have defined two scalars, one of which is solved by the full transport equations (sc.1), the other one (sc.2) is solved by diffusion only. Now think of the domain as a 2D standard rectangular flow channel. Half of it is set as region 1 and the other half as region 2. In between these two regions there is a set of baffles cells with it respective baffle boundaries. At one end of the domain I have got an inlet boundary, where sc1 has a mass fraction of 1 and sc2 has a fixed mass fraction of 1, 100 or 1e6 if you wish (please bare that this scalar is solved by diffusion only, so you can set the value that you want). On the opposite side there is an outlet or a pressure boundary (up to you). I have set the baffle boundary to allow sc1 to flow through it and sc2 to have a zero flux at this boundary.

As far as I am concerned this settings would have to get the job done, but unfortunately they dont:

a) If I let these settings as they are, sc1 will flow only within region 1 and will not be able to flow across the baffle cells, which is not good! Whereas sc2 will diffuse only until it reaches the baffle boundary, which is good.

b) If I set the baffle boundary conditions to have 0 permeability and 100% porosity then sc1 will flow past it, which is good. But it will also let sc2 diffuse across it, which is not good!

Does anybody knows if this is possible to do in StarCD I know it can be done in CFX, but that is only because you can choose freely what to do with the A coefficients. I am pretty sure it can be done in Star but I don't know how. Please let me know if you have know anything that can be done.

Kind regards


ps sorry about the very long message
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