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

Mohsin · July 19, 2011, 03:30

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, 04:29

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, 04:46

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, 03:52

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

kattulanitin · March 5, 2018, 08:47

Hello Mohsin,
How can we calculate?
Np=Number of particles,
Even if we calculate the number of particles by assuming a volume fraction how to input them in fluent?
Thanks and regards,
Nitin K

July 19, 2011, 03:30	Volume fraction of dispersed phase to determine DPM, VOF, Mixture model	#1
Mohsin Senior Member Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 17	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, 04:29		#2
Amir Senior Member Amir Join Date: May 2009 Location: Montreal, QC Posts: 735 Blog Entries: 1 Rep Power: 23	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.

June 7, 2016, 03:52	how to define volume fraction in dpm	#5
mtr94m New Member mohammad Join Date: Jun 2016 Posts: 2 Rep Power: 0	i have slurry jet (water and sediment).i cant define volume fraction for this problem.i define injection from surface..... AHF likes this.

March 5, 2018, 08:47	Volume fraction of dispersed phase to determine DPM	#6
kattulanitin New Member NITIN Join Date: Sep 2017 Location: Warangal Posts: 10 Rep Power: 9	Hello Mohsin, How can we calculate? Np=Number of particles, Even if we calculate the number of particles by assuming a volume fraction how to input them in fluent? Thanks and regards, Nitin K

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July 19, 2011, 04:46		#3
Mohsin Senior Member Mohsin Mukhtar Join Date: Mar 2010 Location: South Korea Posts: 249 Rep Power: 17	Well, Amir, thank you very much for the guidance. Added to ur reputation

January 30, 2015, 13:47		#4
Kanarya Senior Member Join Date: May 2011 Posts: 231 Rep Power: 16	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!