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# When the soil slips away: Mathematical models help understand natural disasters

Date:
June 4, 2014
Source:
Ruhr-Universitaet-Bochum
Summary:
An estimated 600 people worldwide die every year due to landslides, rock avalanches and mudslides. The underlying physical processes are complex and almost impossible to measure. Researchers are studying the flow behavior of granular-fluid mixtures using mathematical models.
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By conducting experiments with glass beads, the continuum mechanics engineers from Bochum refine their theoretical models more and more.

An estimated 600 people worldwide die every year due to landslides, rock avalanches and mudslides. The underlying physical processes are complex and almost impossible to measure. Timo Reisner from the Depatment of Continuum Mechanics studies the flow behaviour of granular-fluid mixtures using mathematical models.

Combining simulation and experiment

The team from the Continuum Mechanics Department collaborates closely with geotechnical engineers from the TU Darmstadt who are studying the flow processes in experiments. They measure, for example, in what way a granular-fluid mixture flows from a three-metre tall container. Timo Reisner simulates this flow process as exactly as possible in mathematical terms. Using a computer, he simulates the velocity of the fluid and grains as they leave the container, the percentage they make up within the mixture and the pressure at different points inside the container. For this purpose, he first has to set up complex equations that describe the behaviour of the grains and the water. He compares the results of the experiment with the results of his simulation and, in case of deviations, modifies the model equations accordingly, until they come close to reality.

Calculations require new software

The equations in Timo Reisner's model are so complicated that they require a powerful arithmetic technique for calculating solutions approximately at the computer. A software programme in which the Bochum researchers' equation system may be implemented does not yet exist. Therefore, the engineers are developing their own programme. Simple processes, for example sedimentation, can already be simulated.

PhD students at the Ruhr-Universität have assisted the "RUBIN" editorial team by contributing articles to the current German and English editions. Timo Reisner is one of the three temporary science journalists; he is doing his PhD at the RUB Research School and presents his research subject in the RUB science magazine, targeting the general audience.

Further information: http://rubin.rub.de/en/international-edition-2014/when-soil-slips-away

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Materials provided by Ruhr-Universitaet-Bochum. Note: Content may be edited for style and length.