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-   -   Volume fraction of dispersed phase to determine DPM, VOF, Mixture model (https://www.cfd-online.com/Forums/fluent/90701-volume-fraction-dispersed-phase-determine-dpm-vof-mixture-model.html)

 Mohsin July 19, 2011 02:30

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

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

 Amir July 19, 2011 03:29

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

 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?