Granular material

Granular matter, also known as a granular medium or granules, consisting of many small solid particles, such as grains or spheres. Examples of this condition are granular materials such as sand, powdered materials such as powder, or in large quantities even loose material such as gravel. It also uses the concepts of mechanical debris and bulk for logistic aspects.

Basics

Important differentiators are that the particles have macroscopic size (these are called materialkundlich grain), to be disturbed neither by quantum effects or thermal motion, and only interact via contact forces ( friction force). It is not a state of matter per se, but about the collective properties of a collection of solids. The most striking feature of granular matter is that they sometimes like a solid behaves - for example, stones lying on sand without sinking - and sometimes like a liquid - that sand fits the form of a vessel and "flows" out when tilting from him.

Physics of granular matter

The physics of granular matter is based on simple mechanical and, at sufficiently small particles, electrostatic interactions. Due to the large number of reactants, however, results in a many-body problem with high complexity, which leads to multiple effects. One example is the Brazil nut effect, where in a mixture of different sized particles, the larger drift to the surface. The properties of granular matter vary greatly when her small amounts are added to liquid, as these reduce the friction of the particles and can lead to cohesion through mutual attraction. This explains about the stability of sand castles.

Granular matter is only in recent years an active area of ​​research, so that explains many phenomena are indeed known from everyday life or physical experiments, but theoretically still not clean.

Alternatively, the mechanical behavior of granular matter also describe the theory of porous media, in this case, the particles are not taken into account individually, but go averaged over its volume fraction in the description.

Areas of application

However, findings in this area can be of great importance for manufacturing processes and storage in the industry.

Another important application is the physics of geophysical mass movements such as debris flows and avalanches, and landslides and sediment in water samples can fall as - are modeled large particles. These models form the basis for award danger zone and disaster protection.

Also in the transport sector is the term loose fill and the underlying machanisch - physical processes of importance, such as for transport safety and stability of cargo ships and aircraft. The explosive effect, dust explosion granular matter - due to high surface oxidation effect and static electricity - was recognized only after serious accidents as a risk factor.