Researchers measure Brazil nut effect in reduced gravity

Apr 09, 2013 by Bob Yirka report
Left: Sketch of the experimental setup. The sample container is attached to an infeed slide, which can be moved vertically on a linear rail. Right: Acceleration profile of the infeed slide and the attached experiment container for an experiment with gamb = gMars. Credit: arXiv:1304.0569 [cond-mat.soft]

(Phys.org) —A combined team of researchers from the Technical University of Braunschweig in Germany and Kobe University in Japan has determined that the Brazil nut effect is less pronounced as gravity is reduced. The team describes tests they undertook both in the lab and as part of a simulated reduced gravity environment aboard an airplane in their paper they've uploaded to the preprint server arXiv, and the results they found after analyzing their observations.

The Brazil nut effect comes from the real world where the largest nuts in a can of mixed nuts—quite often Brazil nuts—tend to rise to the top of the container that holds them during transport. This occurs as the can is shaken—smaller nuts work their way down into smaller open areas, forcing larger nuts to rise towards the surface. The effect has been well studied under normal gravity conditions on Earth, but until now no one has thought to see how it might hold up under conditions such as those that are found on Mars or the Moon.

To find out, the researchers conducted experiments using glass beads rather than nuts—first in the lab, then aboard an A300 Airbus that was repeatedly allowed to descend rapidly enough to counteract the normal pull of gravity. In each case, large 8mm glass beads were put first in a container, followed by smaller 1mm glass beads. As different gravity conditions were met, the containers were shaken and the bead movement inside video recorded.

In analyzing the video, the researchers found that as gravity was decreased, the Brazil nut effect was reduced as well. The larger were more easily able to make their way to the top of the container under normal Earth gravity conditions than they were under reduced gravity conditions that simulated those found on the Moon and on Mars. They noted also that the change was roughly linear.

This research effort was not simply for curiosity's sake—gaining a better understanding of the Brazil nut effect on other bodies under different gravity conditions will likely help scientists gain a better understanding of their underlying structure and could help with such future projects as mining expeditions. The researchers note that other factors could also come into play with the Brazil nut effect in other environments, such as cohesion between particles that could impact the outcome. More research will have to be done to find out if that is the case.

Explore further: Why does coffee spill more often than beer? (w/ Video)

More information: Granular convection and the Brazil nut effect in reduced gravity, arXiv:1304.0569 [cond-mat.soft] arxiv.org/abs/1304.0569

Abstract
We present laboratory experiments of a vertically vibrated granular medium consisting of 1 mm diameter glass beads with embedded 8 mm diameter intruder glass beads. The experiments were performed in the laboratory as well as in a parabolic flight under reduced-gravity conditions (on Martian and Lunar gravity levels). We measured the mean rise velocity of the large glass beads and present its dependence on the fill height of the sample containers, the excitation acceleration, and the ambient gravity level. We find that the rise velocity scales in the same manner for all three gravity regimes and roughly linearly with gravity.

Via TechnologyReview

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User comments : 9

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SteveL
2.7 / 5 (3) Apr 09, 2013
Mmmmmm, moon nuts; every bit as good as earth nuts, but more evenly mixed.
Sean_W
3 / 5 (4) Apr 09, 2013
Yes, the biggest nuts always rise to the top.
nejc2008
3.4 / 5 (5) Apr 09, 2013
Wow!
Are these guys trying to qualify for igNobel Prize?
I wonder who is financing all this.
GSwift7
4.5 / 5 (8) Apr 09, 2013
Are these guys trying to qualify for igNobel Prize?
I wonder who is financing all this.


It seems mundane, and it is in some respects, though this kind of information will be needed before anything meaningful can be done off Earth. There are many engineering problems assiciated with exotic environments. For example, you can't sustain a flame without gravity, since there's no convection to bring new oxygen to the fire. Many of the industrial processes we can take for granted here on Earth are problematic on the moon or in orbit.

All the tables we have compiled regarding how physical systems perform are based on how they perform here. Structural engineering is a good example of this. The load bearing capacity of a structure on the moon would be quite different. For example, a bridge would need to support much less weight, and wind isn't a problem, but a vehicle bouncing up and down on its suspension would still have the same inertia. Everything needs to be re-thought.
Birger
5 / 5 (4) Apr 09, 2013
Big nuts move to the top. I knew that from politics.
lonewolfmtnz
3 / 5 (2) Apr 09, 2013
I want some of that nut dust they're snorting!
Whydening Gyre
1 / 5 (3) Apr 10, 2013
Gswift is right, of course. The actual phenomenon does provide a wealth of useful data for consideration in numerous applications.
But ya gotta admit - it sure sounds like they were partaking in some other South American plant product...
VendicarE
1 / 5 (1) Apr 10, 2013
Look. It's easy.

Brazil nuts are from Brazil and that is south of the equator.

So gravity doesn't pull down there, it pulls up toward the center of the earth which is higher.

As a result Brazil nuts when moved north of the equator continue to be pulled up and away from the equator so they naturally rise the top of the can.

If it wasn't for the fact that they are still pulled down by the moon and the sun, they would float right out of the can and up your nose.

Isaacsname
not rated yet Apr 13, 2013
Granular jamming.......in spaaaaaaaaaaaaaaaaaaaaaaaaaaaace

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