We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune's symmetry axis - that is, over the equivalent transverse dune...

Barchan dunes — crescent-shaped dunes that form in areas of unidirectional winds and low sand availability — commonly display an asymmetric shape, with one limb extended downwind. Several factors have been identified as potential causes for barchan dune asymmetry on Earth and Mars: asymmetric bimodal wind regime, topography, influx asymmetry and dune collision. However, the dynamics and potenti...

Aeolian desert sand dunes birth from wind flow and sand bed interactions: depending on wind properties and sand availability, they can adopt several different shapes from huge motionless star dunes to small and fast mobile barchan dunes. These latter have a characteristic crescentic shape and form on hard ground with low sand supply under a monodirectional wind . Here, a 3d barchan model based ...

Barchan dunes — crescent-shaped dunes that form in areas of unidirectional winds and low sand availability — commonly display an asymmetric shape, with one limb extended downwind. Several factors have been identified as potential causes for barchan dune asymmetry on Earth and Mars: asymmetric bimodal wind regime, topography, influx asymmetry and dune collision. However, the dynamics and potenti...

Aeolian sand dunes originate from wind flow and sand bed interactions. According to wind properties and sand availability, they can adopt different shapes, ranging from huge motion-less star dunes to small and mobile barchan dunes. The latter are crescentic and emerge under a unidirectional wind, with a low sand supply. Here, a 3d model for barchan based on existing 2d model is proposed. After ...

Basically, sand dunes are patterns resulting from the coupling of hydrodynamic and sediment transport. Once grains move, they modify the surface topography which in turns modifies the flow. This important feedback mechanism lies at the core of continuous dune modelling. Here we present an updated review of such a model for aeolian dunes, including important modifications to improve its predicti...

We present detailed shape measurements of several barchan dunes in southern Morocco, near Laayoune. Using these ˆ data, we disprove the concept of shape invariance of barchan dunes of different sizes. Nevertheless, some parts of the barchan dune scale and we try to distinguish these from non-scaling ones. Furthermore, we point out the importance of the exact position of the brink for the overal...

Barchan dunes emerge as a collective phenomena involving the generation of thousands of them in so called barchan dune fields. By measuring the size and position of dunes in Moroccan barchan dune fields, we find that these dunes tend to distribute uniformly in space and follow an unique size distribution function. We introduce an analytical mean-field approach to show that this empirical size d...

Sand dunes are beautiful sand patterns formed by the wind, and have been seen in many places on Mars. In particular barchan dunes, which have a crescent shape, propagate on solid ground under unidirectional winds and are very common on earth’s deserts and coasts, have been observed forming corridors on the floor of martian craters and also on the north pole. However, barchan dunes on Mars have ...

introduction management principles predominated on the development and evolution stages of the geomorphic landscapes are different. this is because of variability in landscape evolution, its relationship with other system components and its response to environmental changes and feedback. one of the most important methods of management of geomorphic landscape is the study and evaluation of morph...