What is MWDiEM (for non-experts)

When we look around us, we can see solid particles everywhere. In the kitchen (e.g. sugar, flour, cereal), in construction (e.g. brick, cement, sand), in nature (e.g. sand, pebbles, sediment in a riverbed), in the industry (e.g. pharmaceuticals, LEGO cubes), etc.. Depending on the context we also call more egzotic structures particles as well, ranging from the planets, asteroids, etc. in space, down to the elementary particles, likes quarks or gluons. However now let's stick with the solid particles we see around us every day. The science that explores how a large number of such classical solid particles interact is called granular science, while the material itself is called granular matter. For example a sand dune consists of a large number of solid sand particles, hence it's a granular system, the salt in your salt holder is a granular system, the pebbles in the riverbed are a granular system. These systems have some very peculiar properties. For example they can segregate: segregation means that based on some physical property of the system when moving the particles wonder to different parts of the system. One very well known example is size segregation. When you have a system consisting of smaller and larger particles, and for example you start shaking the system, the larger particles wonder to the top, while the smaller ones sink to the bottom. Just try it with your muesli box! However there are many other types of segregation (e.g. shape), and some of these are much less understood. 

As already mentioned above we can find a large number of such systems in gravitational mass transport (when mass is moving downslope due to gravity) in nature as well. Just think about a rockfall, rockslide or rock avalanche, where lots of rock boulders are coming down at the same time. Or a snow avalanche, where a multitude of snow particles interact. Or even a debris-flow, where mud is transported downslope. While a rock slide can consist of only two phases (the rocks and the air around and in between them), a debris flow already has 3 phases: the solid particles, water and air in it. 

Project MAWAMOSCA (Mass-waster modelling across scales) is set out to model such dry granular systems that experience gravitational mass transport found in nature. Like the rock slides mentioned above. The method of choice for the study is called Discreet Element Method (DiEM or DEM). This is a numerical modelling method, meaning that it's basically a computer simulation code. In the simulation each and every particle of the system is modelled individually, while these particles can interact. One drawback of the method is that it can only simulate dry systems, thus systems, that don't contain the fluid phase, while the gas phase (air) can be neglected. That is why rock slides are a very good candidate for the project. 

Such simulation software already exists, however most of the times they don't take into account the shape of particles, or more precisely they model each particle as if it would be a sphere. There are already simulation software that can take into account other particle shapes as well, however these are usually non-open source, or not even free. During Project MAWAMOSCA we are developing a simulation software, called MWDiEM, that is able to effectively model a large number of spherical and polyhedral dry granular particles. Once the software is done, we will use it to model some forms of gravitational mass transport systems found in nature, like the rock slides mentioned above. As in these simulations at every timestep the position, the orientation, the velocity, etc. of each and every particle is known, it's possible to basically look inside the system during it's movement. This can be used for example to understand strange runout patterns, e.g. when a rockslide when further down the valley floor then anticipated before, or shape related segregation effects.