The Virtual Sandbox - An approach to introduce principles of granular flow physics in the classroom

When walking on a sandy beach one can observe the drying of the sand below one’s feet. Also, one can think about the stability of sand castles and sand sculptures during the summer holidays. But, what are the physical phenomena that lead to these observations?
The presented work deals with the physics of particles and powders, especially sand as an easy available material for performing experiments in the classroom. Next to real-world experiments, numerical simulations of granular matter are introduced. Thereby, the project shows and supports two important aspects of physics:
1) the importance of performing experiments and simulations during the research process, as well as
2) how modern applications in industry exploit simulations for process design and optimization.
Specifically, we combined elements of inquiry-based learning with results of modern research in the field of granular matter. Thus, leading to lectures based on an experimental approach which are adjustable to the primary and secondary level.
In this lectures students will perform experiments with dry and wet sand. Most important, they first encounter contradictory results due to the peculiar nature of flowing granular matter. For example, students measure the density of wet sand as a function of the water content. They also proof the stability of “sandcastles” made of wet sand samples. The results of their research will be discussed and furthermore supported by some demonstration experiments and microscopic pictures of sand. This ultimately leads to the finding that tiny liquid bridges between the particles must be responsible for this behaviour. These findings also support the next step: the students can compare their results with simulations of these experiments. They get an idea how to simulate such experiments with (i) a simple computer algorithm based on MS Excel, as well as (ii) highly sophisticated parallel computer codes that can be researched by the students at very different educational levels. The virtual sandbox is the final step to illustrate the concept of our project: it is a device which shows the combination of real-world experiments and real-time computer simulations. The simulation results will be immediately projected onto the real-world sand object and the students can immediately interact with simulation.
Besides the presentation of the unit, we will show the impact of the contents on the students’ knowledge about understanding of the basics and the research process, as well as their basic ideas about simulation as a strong tool for modern industrial developments.