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Mohsin July 19, 2011 02:30

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

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:


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.

Amir July 19, 2011 03:29

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.


Mohsin July 19, 2011 03:46

Well, Amir, thank you very much for the guidance. Added to ur reputation:)

Kanarya January 30, 2015 13:47

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!

mtr94m June 7, 2016 02:52

how to define volume fraction in dpm
i have slurry jet (water and sediment).i cant define volume fraction for this problem.i define injection from surface.....

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