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DY: Fachverband Dynamik und Statistische Physik

DY 62: Poster - Dynamics

DY 62.19: Poster

Thursday, March 19, 2015, 16:00–18:00, Poster A

Coarse-grained Simulations of Dune Field Evolution — •Meike Will, Sven Auschra, Marc Lämmel, and Klaus Kroy — Institut für Theoretische Physik, Universität Leipzig, Germany

Crescent-shaped sand dunes, so-called barchans, are among the most impressive structures observed in arid regions on Earth and on Mars. Well established dune models [1] suggest that isolated barchans are unstable when fed by constant sand flux -- they either shrink until they vanish or grow forever. As barchans commonly arrange in large and homogeneous fields, the existence of these assemblies indicates that interactions among adjacent dunes can stabilise them [2].

To investigate the underlying mechanism, we start from an approximate analytical parametrization of the shape and mass evolution of individual barchans [3] and develop a coarse-grained model that explicitly accounts for the wind-driven mass exchange between consecutive dunes. Sand supplied by the horns of upwind followers to a barchan initiates a complex response of its shape and mass. A numerical implementation of the derived model relations is used to simulate large barchan fields. Preliminary results indicate that the dune field, as it advances downwind, converges towards a steady state that is characterized by a fixed point that closely controls dune size and density, thereby reproducing field obsevations.

[1] Kroy, K. et al., Phys. Rev. Lett. 88, 054301 (2002)

[2] Durán, O. et al., Nonlin. Processes Geophys. 18, 455-467 (2011)

[3] Fischer, S. et al., Phys. Rev. E 77, 031302 (2008)