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-   -   DEM - Post Processing - Packing Fraction of particles (https://www.cfd-online.com/Forums/star-ccm/140948-dem-post-processing-packing-fraction-particles.html)

yesaswi92 August 26, 2014 17:03

DEM - Post Processing - Packing Fraction of particles
 
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Hi,

Is there anyway where we can find the packing fraction of particles. I am injecting particles into flow domain and they settle at the bottom of the domain.

Is there anyway, where I can find the packing fraction of the deposited particles?

Also is there a way, where I can get a cross-sectional image of the settle particles? In that way I can see the particle and void space distribution

Thanks a lot.
Yesaswi

ping August 27, 2014 07:21

there is a field function called void fraction in the continuous fluid so use this but you might need to have 2 way coupling enabled for this to have values

to see particles internally use normal methods like a threshold or clipping planes

but be careful on judging packing this way unless you are displaying particles at their real size since they can be scaled up and down like all lagrangian particles

yesaswi92 August 27, 2014 11:49

- I tried to create a report with void fraction as the scalar function. It gives 1 which is definitely wrong. I used both phases separately and together in the parts properties but there is no change. The two way coupling was also 'on' but there was no change. Could to help me in evaluating the value? Also how should the report be? I mean is it volume averaged, sum or any other thing?

- For seeing the particles, I am using clip planes only. But that does not cut the domain and show us a section. So that is the reason I am looking for other way, where I can have a neat cut through the domain such that the particles are also sectioned across the plane.

- While using threshold, what function should I use? Is there a way where I can cut through a plane.

- Regarding the size of the particles, I am using a scalar field (particle size) for the point size.

ping August 28, 2014 04:45

i have tested this in the completed dem tutorial for the conveyor belt as downloaded from steve so it is done correctly

first turn on 2 way coupling then create a new scalar scene and add a section plane to this through the vertical center of the domain and display the field function void fraction

then clear the solution and run again and you will see clearing where the particles are occupying the fluid space even on this very coarse mesh

if you want to report on this voif fraction field then use for example a volume integral report

clipping planes dont seem to work too well on that case so maybe this is problem

but thresholds do

create a new threshold with the grain as the input part and use position z say between .01 and .2 to limit the particle range, and this creates a subset of the particles in that range of z

then add this threshold to a displayer to show them eg the existing scalar scene 1 scalar displayer

yesaswi92 August 28, 2014 12:04

Thanks again for the reply.

The void fraction function worked and I am getting the required reports!!

I tried to play with the thresholds but it is the same like clipping planes. If the particle centroid is outside the threshold range, then the entire particle is chucked out even if a small portion of the particle is still withing the threshold.

I guess I just need to use this option clubbed with void fraction values to extract the information.

Thank you for the help.

ping August 29, 2014 04:18

yes that is the way clipping and thresholds work with particles it appears based on the centroid location probably so you cant display a portion of a particle


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