Small particles are always incomplete !!

souria · May 6, 2016, 08:15

Hello everyone, I hope to find some answers to my problem

I'm tracking particles (surface injection) of different diameters (from 0.3 micro to 200 micro). After calculations, I noticed that most of my particles are incomplete (I injected 10000 and 9000 are incomplete). ..I increased the max. Number of steps in DPM (1e+09, the maximum we can reach in DPM)...but the same results (most particles are incomplete).
So, I tested a group of particles of 6 micro : results all incomplete and another group of 20 micro : results none of them are incomplete !!!

So, my problem is the smallest particles (from 0.3 micro to 19 micro) !! But I don't understand why trajectory calculations are not completed ?? Any answers please ?? !!!

Souria

`e` · May 7, 2016, 04:18

What is your case setup (geometry, flow conditions)? The dominant transport mechanism of particles vary between sizes. For example, submicron particles are diffused by Brownian motion whereas buoyancy forces are more important for larger particles. If your simulation is of a stagnant flow then the submicron particles wouldn't move far as their terminal velocity is negligible (velocity proportional to diameter squared).

souria · May 9, 2016, 04:53

Quote:

Originally Posted by `e`

What is your case setup (geometry, flow conditions)? The dominant transport mechanism of particles vary between sizes. For example, submicron particles are diffused by Brownian motion whereas buoyancy forces are more important for larger particles. If your simulation is of a stagnant flow then the submicron particles wouldn't move far as their terminal velocity is negligible (velocity proportional to diameter squared).

I'm simulated sediment transport in a river ans the flow is steady. Here is an exempel of some data for particle with 6 micro (which are always incomplete) :
u v w diam
-1,25E-01 4,96E-02 -3,65E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,24E-01 5,02E-02 -4,26E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,33E-01 4,63E-02 5,06E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,31E-01 4,79E-02 -2,24E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06
-1,29E-01 4,23E-02 -4,64E-03 6,00E-06

and for 19 micro (where calculation are OK)

u v w
-1,25E-01 4,96E-02 -3,96E-03
-1,33E-01 4,64E-02 4,70E-03
-1,33E-01 4,64E-02 4,70E-03
-1,32E-01 4,64E-02 4,45E-03
-1,32E-01 4,64E-02 4,09E-03
-1,32E-01 4,64E-02 4,10E-03
-1,32E-01 4,64E-02 4,11E-03
-1,32E-01 4,64E-02 4,12E-03
-1,31E-01 4,78E-02 -2,27E-03
-1,31E-01 4,78E-02 -2,26E-03
-1,31E-01 4,79E-02 -2,25E-03
-1,31E-01 4,79E-02 -2,24E-03
-1,31E-01 4,79E-02 -2,23E-03
-1,29E-01 4,30E-02 -4,32E-03
-1,29E-01 4,30E-02 -4,31E-03
-1,29E-01 4,31E-02 -4,30E-03
-1,29E-01 4,31E-02 -4,29E-03
-1,29E-01 4,31E-02 -4,29E-03
-1,29E-01 4,33E-02 -4,10E-03
-1,29E-01 4,33E-02 -4,11E-03
-1,30E-01 5,12E-02 -3,79E-03
-1,30E-01 5,12E-02 -3,79E-03
-1,30E-01 5,12E-02 -3,79E-03
-1,30E-01 5,10E-02 -3,61E-03
-1,23E-01 4,28E-02 1,96E-03
-1,23E-01 4,28E-02 1,96E-03
-1,23E-01 4,28E-02 1,96E-03
-1,32E-01 4,67E-02 2,98E-03
-1,32E-01 4,23E-02 -1,86E-03
-1,32E-01 4,26E-02 -1,73E-03
-1,32E-01 4,26E-02 -1,73E-03
-1,32E-01 4,26E-02 -1,74E-03
-1,32E-01 4,26E-02 -1,75E-03
-1,26E-01 4,74E-02 -9,75E-04
-1,25E-01 4,75E-02 -1,88E-03
-1,26E-01 4,75E-02 -1,89E-03
-1,26E-01 4,76E-02 -1,90E-03
-1,26E-01 4,76E-02 -1,90E-03
-1,26E-01 4,76E-02 -1,91E-03
-1,26E-01 4,76E-02 -1,92E-03
-1,34E-01 4,63E-02 9,13E-05
-1,33E-01 4,93E-02 2,26E-03
-1,33E-01 4,93E-02 2,25E-03
-1,33E-01 4,93E-02 2,25E-03
-1,33E-01 4,94E-02 2,24E-03
-1,33E-01 4,94E-02 2,24E-03
-1,33E-01 4,94E-02 2,24E-03
-1,33E-01 4,93E-02 2,09E-03
-1,33E-01 4,93E-02 2,09E-03
-1,33E-01 4,94E-02 2,08E-03
-1,33E-01 4,94E-02 2,08E-03
-1,33E-01 4,93E-02 2,05E-03
-1,33E-01 4,93E-02 2,04E-03
-1,33E-01 4,93E-02 2,03E-03
-1,33E-01 4,94E-02 2,02E-03
-1,33E-01 4,94E-02 2,01E-03
-1,31E-01 4,76E-02 -2,03E-04
-1,31E-01 4,76E-02 -2,13E-04
-1,31E-01 4,77E-02 -2,23E-04
-1,31E-01 4,77E-02 -2,33E-04
-1,31E-01 4,77E-02 -2,44E-04
-1,31E-01 4,77E-02 -2,54E-04
-1,31E-01 4,77E-02 -2,64E-04
-1,31E-01 4,76E-02 -1,98E-04
-1,31E-01 4,76E-02 -2,05E-04
-1,31E-01 4,76E-02 -2,12E-04
-1,31E-01 4,76E-02 -2,19E-04
-1,31E-01 4,76E-02 -2,26E-04
-1,31E-01 4,77E-02 -2,33E-04
-1,31E-01 4,77E-02 -2,40E-04
-1,31E-01 4,77E-02 -2,47E-04
-1,31E-01 4,77E-02 -2,54E-04
-1,31E-01 4,78E-02 -2,73E-04
-1,31E-01 4,78E-02 -2,77E-04
-1,31E-01 4,78E-02 -2,82E-04
-1,31E-01 4,78E-02 -2,84E-04
-1,31E-01 4,78E-02 -3,09E-04
-1,31E-01 4,78E-02 -3,09E-04
-1,31E-01 4,78E-02 -2,56E-04
-1,31E-01 4,78E-02 -2,66E-04
-1,31E-01 4,78E-02 -2,75E-04
-1,31E-01 4,78E-02 -2,85E-04
-1,31E-01 4,78E-02 -2,95E-04
-1,31E-01 4,78E-02 -3,04E-04
-1,31E-01 4,78E-02 -3,14E-04
-1,28E-01 4,32E-02 -1,11E-03
-1,28E-01 4,32E-02 -1,12E-03
-1,28E-01 4,32E-02 -1,13E-03
-1,28E-01 4,32E-02 -1,14E-03
-1,28E-01 4,32E-02 -1,14E-03
-1,28E-01 4,33E-02 -1,14E-03
-1,28E-01 4,33E-02 -1,15E-03
-1,28E-01 4,33E-02 -1,17E-03
-1,28E-01 4,33E-02 -1,18E-03
-1,28E-01 4,34E-02 -1,19E-03
-1,27E-01 4,59E-02 -3,14E-03
-1,27E-01 4,59E-02 -3,15E-03
-1,27E-01 4,60E-02 -3,07E-03
-1,27E-01 4,60E-02 -3,07E-03
-1,27E-01 4,60E-02 -3,08E-03
-1,27E-01 4,60E-02 -3,08E-03
-1,27E-01 4,60E-02 -3,08E-03
-1,27E-01 4,61E-02 -2,99E-03
-1,27E-01 4,62E-02 -2,98E-03
-1,27E-01 4,62E-02 -2,99E-03
-1,27E-01 4,62E-02 -3,01E-03
-1,27E-01 4,62E-02 -3,02E-03
-1,27E-01 4,62E-02 -3,03E-03
-1,27E-01 4,62E-02 -3,04E-03
-1,28E-01 4,63E-02 -3,00E-03
-1,28E-01 4,63E-02 -3,00E-03
-1,27E-01 4,64E-02 -3,00E-03
-1,27E-01 4,64E-02 -3,01E-03
-1,27E-01 4,64E-02 -3,01E-03
-1,27E-01 4,64E-02 -3,02E-03

I don't know if it helps !!
Thannks

`e` · May 9, 2016, 05:00

What are these velocities corresponding to? Have you tried plotting the trajectories of the particles to determine where they are incomplete after many particle steps?

souria · May 9, 2016, 08:28

Quote:

Originally Posted by `e`

What are these velocities corresponding to? Have you tried plotting the trajectories of the particles to determine where they are incomplete after many particle steps?

They are the velocities (step by step) of a chosen particle.
YEs , I plotted the particles and the position is in the Inlet, seems that didn't move so far ...right now, I try to decrease the time step (if my terminal velocity is lower and my thaupi “relaxation time” is also lower) maybe with the decreasing of my time step I will get something ...

souria · May 9, 2016, 09:44

Quote:

Originally Posted by `e`

What are these velocities corresponding to? Have you tried plotting the trajectories of the particles to determine where they are incomplete after many particle steps?

I just find out something : when I change the calculated scheme, I get no incomplete particles !!
The thing is that, before I used the Runge-Kutta scheme (most performant one) but all particles are incomplete and now, when I use the implicit, it works (no incomplete particles ) ...

I will see if when I combine implicit with Runge kutta it will work !!!
Thank you a lot for your help

Cheers

Souria

May 6, 2016, 08:15	Small particles are always incomplete !!	#1
souria Member souria Join Date: Mar 2013 Location: Nancy Posts: 66 Rep Power: 13	Hello everyone, I hope to find some answers to my problem I'm tracking particles (surface injection) of different diameters (from 0.3 micro to 200 micro). After calculations, I noticed that most of my particles are incomplete (I injected 10000 and 9000 are incomplete). ..I increased the max. Number of steps in DPM (1e+09, the maximum we can reach in DPM)...but the same results (most particles are incomplete). So, I tested a group of particles of 6 micro : results all incomplete and another group of 20 micro : results none of them are incomplete !!! So, my problem is the smallest particles (from 0.3 micro to 19 micro) !! But I don't understand why trajectory calculations are not completed ?? Any answers please ?? !!! Souria

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May 7, 2016, 04:18		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	What is your case setup (geometry, flow conditions)? The dominant transport mechanism of particles vary between sizes. For example, submicron particles are diffused by Brownian motion whereas buoyancy forces are more important for larger particles. If your simulation is of a stagnant flow then the submicron particles wouldn't move far as their terminal velocity is negligible (velocity proportional to diameter squared).

May 9, 2016, 05:00		#4
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	What are these velocities corresponding to? Have you tried plotting the trajectories of the particles to determine where they are incomplete after many particle steps?