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twoPhaseEulerFoam settling velocity of a dilute suspension

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Old   April 10, 2012, 07:54
Default twoPhaseEulerFoam settling velocity of a dilute suspension
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otm
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Hello world!

I have set up a very simple case for the twoPhaseEulerFoam solver (OF-2.1.x). I want to run the very basic case of gravitational settling of a dilute (alpha<1%) suspension of small particles (density=1050 kg/m^3, diameter=100 Ám) in a continous viscous (55 cSt, density 840 kg/m^3) fluid. However, I can't reproduce the expected settling velocity (2.5e-5 m/s). I would expect the particles to instantly get the correct settling velocity, but instead I see a too small but continously increasing settling velocity.

What I expect to see is something like what you can see in a settling experiment in e.g. a test tube, where you get (after some time) from the top down: clean (particle free) contionus phase, an interface moving downwards (direction of gravity) with the settling velocity of the particle phase, suspension of particles with constant=initial concentration, settled particles with high concentration (sludge) at the bottom.

About my case:simpleSettling.gz
I tweaked the "bed" tutorial. Made it 1D. Changed the *properties files as approproiate. No turbulence modelling should be necessary for this case, so I tuned it off. I have tried to turn of packing limiters and played with different BS:s but I can't reproduce the correct settling behaviour.

I would be glad if someone could explain how I should change my setup in order to get the expected result.

BR
Olle
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