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Volume fraction of dispersed phase to determine DPM, VOF, Mixture model

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Old   July 19, 2011, 02:30
Default Volume fraction of dispersed phase to determine DPM, VOF, Mixture model
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Mohsin Mukhtar
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Hello

For using DPM model in fluent, volume fraction of disperesed phase should be below 10% to 12 %, otherwise you have to look for other models such as mixture and VOF models in fluent.

For determining Volume fraction of a particle, the following formula is used:

alpha=NpVp/Vc

where alpha= volume fraction of solid phase
Np=Number of particles
Vp=Volume of particle
Vc= Volume of the container or total volume of the cylinder or the whole control volume.

If alpha comes out to be greater than 12% then "mixture" or "VOF model" would be considered for dense phase.

Please comment if the above statements are correct/wrong.

Thank you so much.
Mohsin
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Old   July 19, 2011, 03:29
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Hi,
The whole idea is right but some other points should be noted:
- Actually this range is not very tight; it's just a rule of thumb, I believe that if Lagrangian modeling could be proper for a case we can use it.
- Note that DPM modeling in FLUENT encounter many bugs in brownian motion and computing deposition, so in many cases in which diffusion term is dominant in dispersion; such as nano-particles, we have to use eulerian modeling, i.e. solving a transport eq. to find particle concentration.

Amir
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Old   July 19, 2011, 03:46
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Well, Amir, thank you very much for the guidance. Added to ur reputation
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Old   January 30, 2015, 13:47
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Hi Amir,

I am simulating gas-solid flow with two fluid approach with fluent and I am trying to have 20% mass loading of the particle at the inlet.
as it is same inlet for both phases area is not important...
my air density is 1.2 kg/m3, velocity is 9.3 m/s.
solid density is 2500 kg/m3 , I think velocity must be calculated but I am not sure or I can use 9.3 for solid as well?
how I can calculate the uniform volume fraction of the solid at inlet while assuming constant particle to gas velocity ratio?
do you have any idea?
thanks in advance!
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