Barchan dunes in the lab

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  • 27 August 2001
Abstract
Dunes dynamics has strong impact on the ecology and the economy of sandy areas, but is far from being understood. Since the work on sand dune formation by R.A. Bagnold, a world wide inventory of dunes has been developed. The most common dune, the so-called barchan, has a typical crescent shape normal to the wind, with arms downwind and forms under mono-directional winds. Various models call for more experimental data. On one hand, field measurements are difficult to perform and often incomplete. On the other hand, it is believed that dunes have a minimal size of the order of one meter, not reducible to smaller laboratory scales. Here we show experimentally that an initial sand pile, under a wind flow charged in sand, flattens and exhibits a typical barchan shape. An evolution law is proposed for the profile and the summit of the dune. The dune dynamics is shape invariant. The invariant shape, the "dune function", is isolated. Our results clearly demonstrates the feasibility of barchan dunes in the lab.

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