UBC Undergraduate Research

Believe It or Nut : Friction and Convection Currents as the Driving Forces of the Brazil Nut Effect Liyanage, Annudesh; Kim, Giuliana


The purpose of this experiment was to propose a comprehensive model to explain the mechanisms behind the Brazil Nut Effect. This is the phenomenon by which the mixing of a granular medium of variously sized particles causes the larger particles to rise and the smaller ones to fall to the bottom. It is speculated that frictional forces between particles and with the container walls in addition to convection currents are the main factors driving this phenomenon. Through measuring the number of shakes required for an intruder particle (the large object) to surface in a granular mixture, this hypothesis was tested by manipulating four different variables: the frictional coefficient between the particles and the container walls, the frictional coefficient among the granular particles, the mass of the intruder, and the volume of the intruder. The results aligned with the trends predicted by the proposed model and therefore may serve as a possible explanation of the Brazil Nut Effect.

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