Particles not been tracked

mack_johnson · March 15, 2013, 14:04

Hi,

I am trying to simulate a human head being sneezed on. My particle inlet is set 0.5m away from the human mouth, with a 20m/s velocity. The partilce injection is a surface injection. the max number of steps is set at 10,000,000. I have meshed the mouth appropriately.

The problem I am encoutering is that the partilces tracks are not picked up. I have set it so 10,000 particles are to be sprayed on to the human head. Though when i run the simulation and go to the particle tracking results only 10% of the particles I input are being tracked. Of those tracked, the majority are also incomplete. Can anyone please help me?

Thankyou,

Mack

A CFD free user · March 15, 2013, 14:58

Hi mack
The success in DPM model to track particles needs somehow trick. First you gotta receive a converged single phase solution which is either gas or liquid, then injecting your particles. I had your problem once, but I did it myself in my case. Stick in your mind that you need to adjust both time step and step size correctly to be able to track all particles. The first thing is that you need to increase the maximum number of steps. There's a rule of thumb, I recall that the multiplication of the numbers of cell in flow direction by step size should be equal to Max number of iteration. Hope it help

sajeesh · April 27, 2013, 06:02

hello....
There's a rule of thumb, I recall that the multiplication of the numbers of cell in flow direction by step size should be equal to Max number of iteration.

i am not getting that.
How i get the number of cells in the flow direction.

two doubts also
what is DPM concentration

It is show that Residence time *mass flow rate of particle /cell volume

What is the meaning of residence time and cell volume...

How exactly i can select certain number of particle in the domain

March 15, 2013, 14:04	Particles not been tracked	#1
mack_johnson New Member Mack Johnson Join Date: Mar 2013 Posts: 1 Rep Power: 0	Hi, I am trying to simulate a human head being sneezed on. My particle inlet is set 0.5m away from the human mouth, with a 20m/s velocity. The partilce injection is a surface injection. the max number of steps is set at 10,000,000. I have meshed the mouth appropriately. The problem I am encoutering is that the partilces tracks are not picked up. I have set it so 10,000 particles are to be sprayed on to the human head. Though when i run the simulation and go to the particle tracking results only 10% of the particles I input are being tracked. Of those tracked, the majority are also incomplete. Can anyone please help me? Thankyou, Mack

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March 15, 2013, 14:58		#2
A CFD free user Senior Member A-A Azarafza Join Date: Jan 2013 Posts: 226 Rep Power: 14	Hi mack The success in DPM model to track particles needs somehow trick. First you gotta receive a converged single phase solution which is either gas or liquid, then injecting your particles. I had your problem once, but I did it myself in my case. Stick in your mind that you need to adjust both time step and step size correctly to be able to track all particles. The first thing is that you need to increase the maximum number of steps. There's a rule of thumb, I recall that the multiplication of the numbers of cell in flow direction by step size should be equal to Max number of iteration. Hope it help

April 27, 2013, 06:02		#3
sajeesh Member sajeesh Join Date: Feb 2013 Posts: 52 Rep Power: 13	hello.... There's a rule of thumb, I recall that the multiplication of the numbers of cell in flow direction by step size should be equal to Max number of iteration. i am not getting that. How i get the number of cells in the flow direction. two doubts also what is DPM concentration It is show that Residence time *mass flow rate of particle /cell volume What is the meaning of residence time and cell volume... How exactly i can select certain number of particle in the domain