Granular materials in geophysics: the dynamics of sand dunes

Erick Franklin

Unicamp | School of Mechanical Engineering, Campinas, Brasil

Salle Structures (Map of the campus)

ABSTRACT

Sand dunes are basically waves or heaps of granular material, appearing under the action of a fluid flow. Of particular interest are barchan dunes (or simply barchans), that are crescent-shaped dunes found in diverse environments, such as river beds, Earth's deserts, and on the surface of Mars. Although presenting roughly the same morphology, the scales are highly different depending on the environment they are in: Their length and time scales are 1 km and 1000 years on Mars, 100 m and 1 year on terrestrial deserts, and 10 cm and 1 minute under water. In all cases, although the scales are different, the dynamics are comparable. In this talk, I will present the main results of our investigations to understand the origin of barchans and how barchan fields emerge. For that, we made use of analytical, experimental and numerical approaches. The analytical part consisted mainly of stability analyses and the numerical part of CFD-DEM simulations. For the experimental part, we took advantage of the much faster scales of aquatic dunes and conducted experiments in a water channel, using lasers and high-definition cameras for measuring the fluid flow and high-speed cameras to measure the dynamics of solid particles. The results are sometimes surprising...