Berlin 2005 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

DY: Dynamik und Statistische Physik

DY 24: Granular Matter

DY 24.8: Vortrag

Samstag, 5. März 2005, 16:00–16:15, TU H2032

Dynamic Scaling of Dune Evolution — •Sebastian Fischer and Klaus Kroy — Abteilung Theorie, Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin, Germany

The beautiful shape of desert dunes is borne out by the complicated interaction between turbulent wind flow and sandy topography. In the case of unidirectional winds and limited sand supply highly mobile crescent–shaped dunes – so–called barchans – form.

In a recent approach, the key mechanisms governing barchan morphology and dynamics were identified and put into a ’minimal model for aeolian sand dunes’. The scale invariance of the turbulent flow is broken by the characteristic scale provided by the sand transport process. As an implication of broken scale invariance we distinguish two kinds of solutions, small sand heaps and larger dunes with a slip face.

We present solutions obtained for various wind and influx conditions. Fixed points of the system, corresponding to shape invariantly moving profiles, are found to be unstable. Dunes of a given volume that are oversupplied (undersupplied) with respect to this steady state grow (shrink). Interestingly, all trajectories obtained for a prescribed influx collapse (up to transients) on a single master curve. Thus the a priory very high–dimensional complexity of state space is significantly reduced. Universal scaling functions that neatly comprise growth kinetics are theoretically derived and numerically confirmed.