Nuts Page
Introduction
This is the new home of the information I made available on completion of the work I did on the Reverse-Brazil-Nut Effect. I've had numerous emails from people asking about the project, and where to find other information, so hopefully this should help.
This site contains the multimedia parts of the project that I had trouble hosting as well as the information that was on the original site and some more info that I'm in the process of adding. You're free to use them as you wish - as long as you credit them back to me.
Background
I shared an office with David Quigley, Dr. Maff Glover et al. And worked with Dr. M. Probert looking at The Reverse-Brazil-nut Effect
The RBNE was a contorversial issue at the time. After its inital theoretical discovery, many experimentalists had trouble finding the effect. A project at York [1] showed that the RBNE did indeed exist, but wasn't able to put the phase transition in the same place as [2].
My breif was to write a computer code for the York group to find out why our own experiments weren't working properly. My results agreed entirely with [2] and also showed how thin the 3rd dimension had to be in the 3-dimensional experiment to be effectivly 2-dimensional. These result can be found in the powerpoint presentation below.
The group was then able to run a very sucessful experiment in the following year[4], taking on some of the ideas that I had found. They were able to confirm the phase transition in the correct position.
[1] V. Booth M.Phys. Project
[2] D.C.Hong et al. Physical Review Letters. Vol 86, No 15
[3] A.P.J. Breu et al. Physical Review Letters. Vol 90, No 1
[4] D. Halls M.Phys. Project
The Brazil-nut Effect
If you take a bag of Brazilnuts and Hazelnuts and shake it what happens? Well, the Brazil-nuts go to the top, and the hazlenuts go to the bottom (The Brazil-nut Effect). At a certain density and size &.c. the opposite is true, (The Reverse Brazilnut Effect). I wrote a program, in Fortran, to model this situation and find out what the critical points are.
The Brazil-nut effect (BNE) is a well known phenomenon whereby a bag of mixed nuts (and more importantly any granular matter) seperates on shaking. The larger particles, (i.e. Brazil-nuts) go the top, and the smaller ones (say: hazel-nuts) go to the bottom. The movies again can be found at the bottom of the page.
Here are 3 frames from a movie I made. The radius ratio between the two spheres was 2 and the mass ratio was 1 (i.e. they both have the same mass.)
They start out at random locations.
Bounce around a bit...
...and finally settle with the larger ones at the top.
The Reverse Brazil-nut Effect
In 2001 Hong et al [2] published a paper reporting the Reverse Brazil-nut effect there was some contoversy at the time between experimentalists, as to whether the effect existed, but it was finally shown to exist by A.P.J. Breu et al [3] in January 2003. Here again are my Povray images of the RBNE this time. Again we set off from a random position
Once again they're allowed to bounce around a bit.
But this time, the big ones end up on the bottom.
Why, because the masses are different. True the radius ratio is still 2 but this time I have set the mass ratio to 7
Movies
Beware most of these movies are around 20MB.
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The Brazil-nut effect
Here the As have a r=2 and m=1. There are 75 of each colour.
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The Reverse Brazil-nut effect
Here the As have a r=2 and m=8. There are 75 of each colour.
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The Brazil-nut effect (With purple ones ontop)
Here the As have a r=2 and m=1. There are 75 of each colour.
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Mixed State
Here the As have r=1.732 and m=3 to force them onto the transition line. There are 75 of each colour.
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RBNE (With purple ones ontop)
Here the As have a r=2 and m=8. There are 75 of each colour.
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RBNE (With purple ones underneath)
Here the As have a r=2 and m=8. There are 75 of each colour.
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The Reverse BrazilNut Effect - Big
Here the As have a r=2 and m=7. There are 500 of each colour. N.B. I changed the colour here to make them prettier.
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