On the crescentic shape of barchan dune

TL;DR

This paper introduces a 3D model for crescent-shaped barchan dunes, revealing how dune shape influences sand flux through a non-linear diffusive process driven by wind and sand interactions.

Contribution

It presents a novel 3D modeling approach based on existing 2D models, incorporating lateral sand flux deflection due to dune shape.

Findings

Lateral sand flux is influenced by dune shape.

The model captures the crescentic form of barchan dunes.

Non-linear diffusion describes sand movement around dunes.

Abstract

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 describing the intrinsic issues of 3d modeling, we show that the deflection of reptating particules due to the shape of the dune leads to a lateral sand flux deflection, which takes the mathematical form of a non-linear diffusive process. This simple and physically meaningful coupling method is used to understand the shape of barchan dunes.