For the first time, a team of scientists from the University of Manchester in England has captured the complicated dynamics that cause the largest nuts to rise to the top, which is commonly known as the ‘Brazil nut effect’ — the phenomenon of particles segregating by their size. Scientists, in a video, have captured the complex dynamics of particle movement in granular materials. They explained why mixed nuts often see the larger Brazil nuts gather at the top. The findings of the scientists could have a vital impact on industries struggling with the ‘Brazil-nut effect’ phenomena, such as pharmaceuticals and mining.
It is being commonly observed that, if we dip our hands into a bag of mixed nuts, we will only find the Brazil nuts at the top. In cereal boxes too, the larger items rise. The ‘Brazil-nut effect’ has huge implications on the industries where uneven mixing affects the quality of products.
According to a new research published in the journal Scientific Reports, scientists have used time-resolved 3D imaging to show how Brazil nuts rise upwards through a pile of nuts.
The scientists captured the unique imaging experiment on video showing the temporal evolution of the nut mixture in 3D. Peanuts are seen to percolate downwards whilst three larger Brazil nuts are seen to rise upwards. The first Brazil nut reaches the top 10% of the bed height after 70 shear cycles, with the other two Brazil nuts reach this height after 150 shear cycles. The remaining Brazil nuts appear trapped towards the bottom and do not rise upwards.
Explaining the process, Regius Professor Philip Withers said the team followed the motion of the Brazil nuts and peanuts through time-lapse X-ray Computed Tomography as the pack was repeatedly agitated.
“This allowed us to see for the first time the process by which the Brazil nuts move past the peanuts to rise to the top,” he said.
Dr Parmesh Gajjar, the lead author of the study, said that their study highlights the important role of particle shape and orientation in segregation.