Granular convection

The Brazil nut effect occurs in mixed granular media. It can be found after repeated shaking to a package that contains particles of different sizes, the largest above.

The term comes from everyday life: When you open a pack of cereal or mixed nuts, the biggest nuts are usually on top. Since the thickest pieces in the cereal in the U.S. often brazil nuts (English: brazil nuts ) are, this phenomenon is also known as Brazil nut effect. In technical terms it is a separation or segregation.

The reason for the segregation of different sized components is transportation. By shaking motion are briefly created voids into which preferred the smaller components of cereals slip. The larger will not fit into it, so that they effectively up " hike ", the longer you shake.

The exact way the nuts depend on their density, shape and surface texture as well as the outer movement. It may also be that the thick nuts on the bottom. One then speaks of the reverse Brazil-nut effect.

The Brazil nut effect not only plays a role in cereal, but for the dynamics of all granular media and thus about in geophysics and geotechnical engineering in terms of sandy and gravelly soils of importance. To date, this phenomenon is a dissolved only rudimentary physical problem.