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

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 July 19, 2011, 02:30 Volume fraction of dispersed phase to determine DPM, VOF, Mixture model #1 Senior Member   Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 8 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

 July 19, 2011, 03:29 #2 Senior Member     Amir Join Date: May 2009 Location: Montreal, QC Posts: 739 Blog Entries: 1 Rep Power: 14 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 pasargad64 likes this.

 July 19, 2011, 03:46 #3 Senior Member   Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 8 Well, Amir, thank you very much for the guidance. Added to ur reputation

 January 30, 2015, 13:47 #4 Senior Member   rkhr Join Date: May 2011 Posts: 226 Rep Power: 7 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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