Why Brazil Nuts are on Top: Size-Segregation in a Vibrated Granular Medium

Synopsis

If you recently opened up a can of mixed nuts, there is a good chance you found the Brazil nuts on top. In general, granular mixtures that have been shaken usually end up with the largest particles at the top, even if they are denser than the rest. This unusual phenomenon of size segregation has been coined the Brazil Nut Effect (BNE) and has been the focus of many studies over the last few decades due to its wide applications in industrial processes. Even though the effect is easy to demonstrate with household items, the underlying physics of the BNE is complex and has yet to be fully understood. In this talk, I will discuss a series of experiments that display the potential mechanisms behind the BNE, as well as the limitations of these descriptions.