Which method does EDEM use with "volume packing"?

Raheem Sterling_22160

Hi，

I have tried with volume packing to create a seris of porosity packings, but when I calculate loacl fraction with ''volume of particle/volume of cell which created by voronoi cell", local fraction was very different from packing porosity especially in loose packings.

So I am thinking about method of "volume packing".

Thanks for help!

Stefan Pantaleev_21979

Hi Raheem,

 

What is the size of your cells relative to the particle size? EDEM gives particle positions in terms of the centre of mass of the particle so if particles are large and cells small you can have a large particle skew the results in a cell, because all of its mass is considered inside the cell while a large portion might actually not be. Do you get the correct porosity when considering a single cell containing all the particles?

 

Best regards,

Stefan

Raheem Sterling_22160

Stefan Pantaleev_21979 said:

Hi Raheem,

 

What is the size of your cells relative to the particle size? EDEM gives particle positions in terms of the centre of mass of the particle so if particles are large and cells small you can have a large particle skew the results in a cell, because all of its mass is considered inside the cell while a large portion might actually not be. Do you get the correct porosity when considering a single cell containing all the particles?

 

Best regards,

Stefan

Hi, Stefan,

 

The cell I calculated with open source code "voro++", the results showed the relative size of cells to particle size has a large distribution. Please see the attached figure, it's a slice of model,  magnitude of solid fraction（frac） was showed by color, my target value of frac was around 0.4.

By the way, what do you mean about correct the porosity in EDEM? I just saw the settings in "volume packing" like "position correction" and "position optimisation".

 

Kind regards!

Raheem

Stefan Pantaleev_21979

Raheem Sterling_22160 said:

Hi, Stefan,

 

The cell I calculated with open source code "voro++", the results showed the relative size of cells to particle size has a large distribution. Please see the attached figure, it's a slice of model,  magnitude of solid fraction（frac） was showed by color, my target value of frac was around 0.4.

By the way, what do you mean about correct the porosity in EDEM? I just saw the settings in "volume packing" like "position correction" and "position optimisation".

 

Kind regards!

Raheem

With this porosity calculation approach you will always see this kind of vairance if you have a wide PSD for the cells and particles. It's likely not real in the bed but an artifact of the calculaton you are doing in the cells as per my previous comments about what particles are counted as being part of the cell. To resolve this you need to move to a proper continuum calculation of the solid fraction. See these papers:

Goldhirsch, I. (2010) ‘Stress, stress asymmetry and couple stress: From discrete particles to continuous fields’, Granular Matter, 12(3), pp. 239–252. doi: 10.1007/s10035-010-0181-z.

Tunuguntla, D. R., Thornton, A. R. and Weinhart, T. (2016) ‘From discrete elements to continuum fields: Extension to bidisperse systems’, Computational Particle Mechanics. Springer International Publishing, 3(3), pp. 349–365. doi: 10.1007/s40571-015-0087-y.

Labra, C., Ooi, J. Y. and Sun, J. (2013) ‘Spatial and temporal coarse-graining for DEM analysis’, AIP Conference Proceedings, 1542(4), pp. 1258–1261. doi: 10.1063/1.4812167.