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-   -   chtMultiRegionFoam: fluid-fluid interface (http://www.cfd-online.com/Forums/openfoam/101413-chtmultiregionfoam-fluid-fluid-interface.html)

samiam1000 May 3, 2012 08:38

chtMultiRegionFoam: fluid-fluid interface
 
Dear All,

I am trying to use the different tutorial that deals with the chtMultiRegionFoam solver, but I can not find what I am looking for.

I see hot to treat the fluid-solid interface between region, but I can not understand how to treat the solid-solid and the fluid-fluid interface.

Which are the right BC on epsilon, k, U, p, p_rgh, T and so on on these interfaces?

Thanks for help,

Samuele

anon_a May 3, 2012 10:01

I will attempt to answer your question, not because I am sure about the answer but rather to see if I have it right in my mind.

In the chtMultiRegionFoam/multiRegionHeater we can see that all interfaces of the heater with the rest of the parts have the same BC for the temperature:
Code:

            "heater_to_.*"
            {
                type            compressible::turbulentTemperatureCoupledBaffleMixed;
                neighbourFieldName T;
                K              solidThermo;
                KName          none;
                value          uniform 300;
            }

Since the heater is a neighbour of both the gas and the solid, I believe this answers your question about solid-solid: you use pretty much the same BC as in solid-gas. If I remember well, this just imposes the same temperature and heat flux on both sides. The rest of the quantities you wrote about (epsilon, k, U, p, p_rgh) do not exist in the solid anyway.

As for the fluid-fluid: why do you have an interface in the first place? Can't you join these two parts? if you can't, you might need significant modifications in the solver.

samiam1000 May 3, 2012 10:13

Dear anon_a,

thanks for answering.

Actually, as far as the solid-solid interface is concerned, you're right. It's enough to use the same BC that are used in the tutorial.

Also, I have 2 different fluid region because I would like to be able (but I need to modify the solver and I've not been able, yet) to impose the temperature in a certain FLUID volume, which is connected with another fluid volume. Altough I can't run my new solver, yet, I have a mesh with 2 detached fluid regions, with an interface. I thought that a zeroGradient condition was ok, but that's not true.

The simulation, in fact, seems to explode and it's like a source appear on the interface.

Anyother idea?

Do you think I should `unify the 2 regions'? Can't I deal a domain with to fluid regions detached by an interface?

Linse May 3, 2012 10:32

Hi Samuele,

If it really is just about imposing a different temperature on one of two fluid zones, I suggest using the "setFields" utility. That is much easier than writing a new solver, getting two zones to cooperate easily.

Nevertheless, if you made progress on the fluid-fluid-thingy, I would be happy if you could share your knowledge with me. Because at the moment I am trying to do something very similar. ;-)

samiam1000 May 3, 2012 10:39

Dear Bernhard,

of course I will share what I will discover.

And what about the setField? I need to impose temertature, but I need that it remains constant during the whole simulation. I was thinking about explicitSetValue (but it's not implemented in the multi regions solver). That's why I was editing the source.

Can I solve this with the setFields option?

Also, what about writing via email (samuele.zampini@gmail.com)? That would be much easier and we could post something useful if we reach our goal.

Samuele.


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