Almost fifty years of investigations of barchan dunes morphology and dynamics is reviewed, with emphasis on the physical understanding of these objects. The characteristics measured on the field (shape, size, velocity) and the physical problems they rise are presented. Then, we review the dynamical mechanisms explaining the formation and the propagation of dunes. In particular a complete and or...

Many barchan dune corridors appear to contain dunes of stable size and spacing [1], and dune fields often exhibit regular patterns [2, 3] with apparent characteristic size and spacing (figure 1). It is still an open question as to what sets this characteristic scaling – local conditions such as topography or sand supply, or common dynamic processes such as those relating to saltation. Additiona...

The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show, by means of numerical simulations, that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the...