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twoLiquidMixingFoam: validation

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Old   April 8, 2014, 17:50
Default twoLiquidMixingFoam: validation
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Hello everybody.
I'm trying to learn how twoLiquidMixingFoam works and also how fine the solution is, so I run a very simple test case, reproducing famous experiment by Reynolds.
In order to see if the solver works properly, I imposed a zero diffusivity between the two species and a laminar flow (turbulence off, Dt ab =0). Re number is around 100 and the duct is quite short.
In my opinion this should mean that the two liquid are completely non-miscible and so the should be transported w/o any mixing, i.e. the transport equation becomes:

ddt(alpha1)+div(phi,alpha1) == 0

What I actually got looks quite strange to me. I attached a picture of the solution. As you can see, there's a wide region of mixing between the two liquids.
On the other hand, I implemented a steady state transport eq in simple algorithm ( div(phi,a) == 0 ) and solved a similar case ("a" is a non-reactive non-diffusive passively transported scalar used as a marker. In that case I actually got that "a" is simply transported w/o mixing, as I supposed.

The case definition is attached .

Can you please help me? Am I wrong or is it a solver fault?

Thank you in advance

Federico
Attached Images
File Type: jpg 2liqMix.jpg (71.2 KB, 38 views)
File Type: jpg alpha1.jpg (49.7 KB, 31 views)
Attached Files
File Type: zip 2liq.zip (9.3 KB, 9 views)
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