Sphere-Packing porosity development

[Marku]

If you have a large collection of hard sphere's and drop them into a bucket, then shook the bucket, would the sphere's rearrange themselves into a more tightly packed state i.e. lower porosity.

 

[Studiot]

Hello, marku, welcome to physics forums.

That's a strange question as it surely depends how you dropped them in in the first place.

Perhaps if you told us more about the background to this question you might get a better answer.

 

[Marku]

Thank you. I mean randomly dropped, for example poured using another bucket. Or another example maybe if using a computer you randomly generated the position of the particles in mid-air in a volume (with walls i.e. bucket), then you let the spheres settle (according to gravity), and began shaking.

 

[Studiot]

Well that isn't much background to go on.

I don't know if you are aware there is a theoretical maximum packing density of spheres (minimum insterstitial voids).

This corresponds to one of the crystal structures, but there are other stable structures.

But then you might be interested in the mechanism by which the spheres pack down.
This is used in defect theory in materials science.

Both subjects occupy whole books.

Then again the above generally concentrates on the material present. Your question was in terms of the voids.
This is often discussed in soil mechanics or concrete mix design.

So what are your thoughts?

 

[sir_manning]

This might be helpful: http://en.wikipedia.org/wiki/Kepler_conjecture "Experiment shows that dropping the spheres in randomly will achieve a density of around 65%". I think how much they settle down would depend on the size of the balls and the diameter of the bucket.

 

[Studiot]

Good link that!