Emergence of a barchan belt in a unidirectional flow: Experiment and numerical simulation

We observed the time evolution of dune fields in a water tank experiment and simulated it by using a simple model without taking complex fluid dynamics into account. The initial sand bed changed its form to transverse ripples, that is, dunes with straight crest lines perpendicular to the flow direction. Then crescentic dunes, called barchans, evolved from transverse ripples.