When Sand Behaves Like Oil


Sand, rice and coffee are all examples of granular materials.

Sand, rice and coffee are all examples of granular materials. The behaviour of granular substances plays a key role in many natural processes, such as avalanches and the motion of sand dunes, but they are also important in industry. In the manufacture of pharmaceuticals or foods, it is important to process granular materials as efficiently as possible.

Despite the variety of practical applications, the physical laws that govern how granular materials behave are only partly understood. The opposite is true in the case of liquids: a number of well-established physical laws and mathematical instruments are used to describe their behaviour. This is particularly true for unstable, complex mixtures, such as emulsions, which have structures that quickly rearrange themselves.

A new order

Researchers from the group led by Christoph Müller, Professor of Energy Science and Engineering at ETH Zurich, in collaboration with scientists at Columbia University in New York, have discovered that under certain circumstances, mixtures made of granular materials exhibit striking similarities to mixtures of immiscible liquids and can even be described by similar physical laws.

Read more at ETH Zurich

Image: Under certain conditions, granular materials behave like liquids and form similar shapes. (CREDIT: ETH Zurich / Alexander Penn)