Growth of barchan dunes of bidispersed granular mixtures

TL;DR

This study experimentally investigates the growth and internal structure of subaqueous barchan dunes composed of bidisperse grains, revealing segregation patterns and surface stripes driven by fluid entrainment and grain rolling properties.

Contribution

It introduces new experimental insights into how bidisperse grains influence barchan dune morphology and segregation, highlighting the roles of fluid entrainment and grain mobility.

Findings

Grain distribution within dunes varies with grain pair used.

Transient stripe patterns form on dune surfaces.

Segregation occurs through a diffusion-like mechanism.

Abstract

Barchans are dunes of crescentic shape found on Earth, Mars and other celestial bodies, growing usually on polydisperse granular beds. In this Letter, we investigate experimentally the growth of subaqueous barchans consisting of bidisperse grains. We found that the grain distribution within the dune changes with the employed pair, and that a transient stripe appears on the dune surface. We propose that observed patterns result from the competition between fluid entrainment and easiness of rolling for each grain type, and that grains segregate with a diffusion-like mechanism. Our results provide new insights into barchan structures found in other environments.