Inconsistency in DPM concentration

Mat_fr · November 15, 2012, 10:28

Dear all,

I'm using the DPM model of FLUENT, with the following parameters :
* unsteady
* two-way coupling (but without resolving the flow equations. Thus, im only resolving the particles motion equation in a one way coupling approach)
* inert particles (no mass, no heat, transfers)

In this context, I was monitoring the DPM_CONCENTRATION average on a surface, and I saw some inconsistencies.

Thus, I did a small test, by computing the total mass of particles in my domain (sum over all the cells of DPM_CONCENTRATION*CELL_VOLUME), and I get the following results :

at injection : mtot = 5.44e-10 kg
after 1s : mtot = 5.29e-10 kg
after 3s : mtot = 4.72e-10 kg
after 5s : mtot = 5.0e-10 kg
What is happening ??? Ok there can be some numerical diffenrences, but not so much!
There are no particles escaping (always the same number as initially), and I don't have any mass transfer. So, what did I miss ?

Thanks a lot for your help !

Best,

Mat

sajeesh · April 27, 2013, 07:20

[QUOTE=Mat_fr;392284]Dear all,

Thus, I did a small test, by computing the total mass of particles in my domain (sum over all the cells of DPM_CONCENTRATION*CELL_VOLUME), and I get the following results :

at injection : mtot = 5.44e-10 kg
after 1s : mtot = 5.29e-10 kg

sir how you r calculating this.....what is sum over all cells of DPM concentration.how you get that..
what is cell volume
how you get this total mass..
i am fed up with this my problem to finding out the number of particle in my domain...or other wise i want to set a 3 particle in the domain,,how i can do that

Help me please.....

November 15, 2012, 10:28	Inconsistency in DPM concentration	#1
Mat_fr Member Mat Join Date: Jan 2012 Posts: 60 Rep Power: 14	Dear all, I'm using the DPM model of FLUENT, with the following parameters : * unsteady * two-way coupling (but without resolving the flow equations. Thus, im only resolving the particles motion equation in a one way coupling approach) * inert particles (no mass, no heat, transfers) In this context, I was monitoring the DPM_CONCENTRATION average on a surface, and I saw some inconsistencies. Thus, I did a small test, by computing the total mass of particles in my domain (sum over all the cells of DPM_CONCENTRATION*CELL_VOLUME), and I get the following results : at injection : mtot = 5.44e-10 kg after 1s : mtot = 5.29e-10 kg after 3s : mtot = 4.72e-10 kg after 5s : mtot = 5.0e-10 kg What is happening ??? Ok there can be some numerical diffenrences, but not so much! There are no particles escaping (always the same number as initially), and I don't have any mass transfer. So, what did I miss ? Thanks a lot for your help ! Best, Mat

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April 27, 2013, 07:20		#2
sajeesh Member sajeesh Join Date: Feb 2013 Posts: 52 Rep Power: 13	[QUOTE=Mat_fr;392284]Dear all, Thus, I did a small test, by computing the total mass of particles in my domain (sum over all the cells of DPM_CONCENTRATION*CELL_VOLUME), and I get the following results : at injection : mtot = 5.44e-10 kg after 1s : mtot = 5.29e-10 kg sir how you r calculating this.....what is sum over all cells of DPM concentration.how you get that.. what is cell volume how you get this total mass.. i am fed up with this my problem to finding out the number of particle in my domain...or other wise i want to set a 3 particle in the domain,,how i can do that Help me please.....