When engineers play in the sandbox!
Summer, sun, sand castle
Beach vacation is popular with Germans
In addition to city breaks, hiking vacations and cruises, beach vacations are the most popular type of vacation for Germans in the summer. According to statistics from the German Travel Association, 72.4% of trips of more than 5 days lead abroad. 36.9% of these are vacations to the Mediterranean.
Who can blame them: Relaxing in the sun on the sandy beach not only helps to escape the stressful everyday life, it is also a dream for our children. For the little ones, there is nothing better than playing in a large natural sandbox and building sand castles. While some are more reminiscent of ramshackle shacks, other structures win prizes and titles in worldwide competitions. Sad only when a ball comes flying ...
Sand as a building material: Are there physical limits to the imagination when building castles?
The question could only come from our engineers. Back in the sandbox at our age not only sounds tempting, it convinced us!
Without precise data, one can only speculate about the stability of sand castles. It depends on the moisture, the grain size and the type of sand. Only with water does sand become a suitable building material. Considering the surface tension and the optimal sand conditions, a sandcastle with a basic radius of 20 cm can grow up to 2.50 m high. At least, this is the result obtained by students at the University of Amsterdam.
Why does wet sand hold better than dry sand?
We think everyone has asked themselves this question at some point. But the explanation is relatively simple. Sand consists of tiny grains of sand that do not offer each other any grip. By adding water, small bridges are created between the particles. These water bridges hold the grains together by their surface tensions. As long as their own weight does not destroy the water bridges, the structures will remain standing!
"A lot helps a lot!", you might now think. We say, "No!". Too much water makes the grains float and the stability is lost again.
For all the theory: When a ball comes flying, it's too late anyway!
Total destruction! A short carelessness of the children playing with the ball and the dream of their own castle is gone. A sand castle can withstand only a few external impacts. Is it possible to calculate this incident? Of course, the magic word is particle simulation!
The particle simulation as an all-purpose weapon
For what is it used?
The calculation was solved with a particle simulation. This type of simulation is divided into SPH (Smoothed-particle hydrodynamics) and DEM (Discrete Element Method).
The SPH method
Astrophysics, ballistics and tsunami calculations are also frequently mentioned with the SPH method. It can be used to represent extreme deformation conditions and the separation of materials. The advantage is that there are no distorted elements. In addition, elements are not erased when damaged, allowing for more realistic imaging of penetration of various components. In addition, the particles can be used to include liquid or gaseous media in dynamic calculations (e.g. drop tests of filled containers).
In fluid mechanics, 2-phase flows can be represented by particles. Here, the methodology is suitable for making statements about the distribution of fluids, e.g. in the lubrication of gears.
The DEM method
DEM is used for flows with a very high number of particles, as the method is very powerful and robust. Here, all sizes and shapes of particles can be described. In structural mechanics, the effect of the bulk material on surrounding components can be investigated. Examples of application areas are:
- Simulation of the behavior of atoms and molecules
- Development of processing methods for bulk materials in silos, e.g. grain
- Development of processing methods for bulk raw materials, e.g. sand, cement, gravel
- Simulation of dust generation and material loss, e.g. toner, tablet coating
- Simulation of geodynamics processes, e.g. dynamics of accretionary wedges
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