Controlling pore sizes in sphere packings

Hello,

Are you referring to the properties of a PFV network? You can control the sphere size distribution [1][2] in yade.

Cheers,

Robert

[1]https://yade-dem.org/doc/yade.pack.html#yade._packSpheres.SpherePack.makeCloud
[2]https://answers.launchpad.net/yade/+questions?field.search_text=psd&field.sort=RELEVANCY&field.sort-empty-marker=1&field.actions.search=Search&field.language=en&field.language=fr&field.language-empty-marker=1&field.status=OPEN&field.status=NEEDSINFO&field.status=ANSWERED&field.status=SOLVED&field.status-empty-marker=1

Hi Robert,

I'm talking about arranging the positions of the spheres to match the actual porous material that I'm modeling. So the location of voids and the connectivity of the pores inside the DEM model should be the same as the actual sample. Not sure if that is possible but I just wanted to check if this is doable.

Thanks,
Othman

Hi Othman,

it depends on definitions of many terms ("same", "pore", "network")..

Could you please provide some more information?
- What scale you simulate?
- What is typical pore size / pore structure of your sample?

thanks
Jan

If you have grain positions from a specimen imagery, you can place spheres in those positions with one or two commands in yade. I’m unsure if this is what you seek though.

Jan,

My actual specimens are 100 mm diameter by 200 mm height. Pore sizes are 0.5~3 mm.

Robert,

Yes that's what I seek and I have x-ray slices/images of the actual sample. Would you elaborate more on the Yade commands that you mentioned?

Thanks,
Othman

Something like

O.bodies.append(sphere( (xC,yC,zC),radius )) # with xC,yC,zC the coordinates of the center, and radius the .. radius, as given by your imagery

?

Jérôme,

Thanks for your answer but I'm not sure if I understand what you're providing. So you mean to import a 3D volume of the actual sample and fill the solid part with spheres?

If you see Fig. 1-b in [1], I'm trying to fill the solid part (the aggregates) with spheres so that I have a DEM model with exact pore network as the real sample (from imagery).

[1] https://www.sciencedirect.com/science/article/pii/S0950061817323681

Oh, it all makes sense...only 7 comments into the thread :-)

If I were you I would make a grid of boolean points in your imagery data characterized by solid or pore. Then I would isolate the grid points characterized by "pore". Now take those coordinates and use them to delete spheres (i.e. if a sphere is a certain distance from a pore grid point, it should be deleted) from a dense packing in Yade. I think that would be your best bet.

Coincidentally, I am working on a very similar imagery data extraction followed by Yade data injection process in the coming days. My plan is to use ImageJ to extract the grid point data and then probably feed that txt file directly into C++ for characterizing pore spaces.

Robert,

That's really helpful. Thanks a lot for sharing this idea. Just a quick question, when I delete spheres based on pores grid point " if a sphere is a certain distance from a pore grid point, it should be deleted", pores have different sizes, so if I specify fixed distance that if a sphere is within, the sphere will be deleted, then I will end up having constant pore size. Any idea how to fix that?

Thanks
Othman

Happy to help ;-)
I dont think that will be an issue. It is my impression that you will have many grid points within the pore spaces. Bigger pores will contain more grid points, thus they will be larger. The sphere delete buffer won't impact that.

Sounds great. Thank you all for your help. Problem solved.

Regards,
Othman