Berlin 2012 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 21: Granular Matter/Contact Dynamics
DY 21.8: Vortrag
Mittwoch, 28. März 2012, 16:15–16:30, MA 144
Sorting of sand grains inside migrating dunes — Christopher Groh1, Ingo Rehberg1, and •Christof A. Krülle1,2 — 1Experimentalphysik V, Universität Bayreuth, D-95440 Bayreuth, Germany — 2Maschinenbau und Mechatronik, Hochschule Karlsruhe - Technik und Wirtschaft, D-76133 Karlsruhe, Germany
In general, agitated granular matter is known to show de-mixing whenever particles differ in size, shape or density. For example, inside natural sand dunes grain sorting phenomena are well-known features for geomorphologists coined reverse grading, when larger particles are found on top of smaller ones. Already in 1993 Anderson & Bunas demonstrated the effect of size segregation in a migrating dune by modeling the trajectories of large and small particles with a stochastic cellular automaton. Larger, and therefore heavier, grains travel in small jumps of the order of a few grain diameters, while smaller particles are able to leap over the crest far down into the shadow zone. Consequently, smaller particles end up being buried by larger ones at the toe of a dune. In addition, Makse (2000) showed that this size segregation due to different hopping lengths in the wake of a dune competes with a so-called shape segregation during transport and rolling of particles with different roughness along the dune's surface. Here we report results of an experimental investigation where the particles inside a downscaled model dune differ not in size or shape but in density, revealing that also denser particles accumulate on top of lighter ones and will finally end up close to the crest of a migrating dune [1].
[1] C. Groh, I. Rehberg, C.A. Kruelle, PRE 84, 050301(R) (2011).