Scientists have performed detailed simulations of the formation of tiny dune-barchans that form on the seabed. In this way, they were able to trace the trajectories of individual sand grains under the influence of water currents. In the future, the results of the study can be used to describe a more long-term evolution of large dunes in the deserts of Earth and Mars.
Scientists from the University of Campinas (Brazil) and the University of California at Los Angeles (USA) studied the formation of dunes in detail. This is the name given to dunes - sand hills formed by the wind and shaped like a crescent moon. This type of relief is represented in a wide variety of landscapes and sizes. Tiny barchans only a few centimeters long are formed at the bottom of the ocean, in the deserts of Earth, and on the surface of Mars they spread out over many kilometers and reach hundreds of meters in height.
Until now, scientists have not carried out calculations and model the growth and evolution of barchans, which can form for years on Earth and thousands of years on the Red Planet. Calculations tracing every grain of sand on a barchan remained impossible. Now, however, the researchers have been able to do so with tiny dunes on the ocean floor, which form much faster under the influence of water than barchans on land.
They used CFD-DEM (Computational Fluid Dynamics/Discrete Element Method) simulations to determine the morphology of the barchans, describe the movements of individual sand grains and the parameters of fluid flows affecting them. The results of the study are presented in the journal Physics of Fluids.
The authors applied equations of motion to each grain of a tiny barchan deformed by fluid flow. The simulation results were compared with the behavior of real barchans in an aqueous environment.
The study paves the way for further study of barchan formation. Changes of Martian and terrestrial terrain under the influence of the wind occur on a much larger time and distance scale than in the water environment, in which dunes of a few centimeters in length appear in a matter of minutes. Nevertheless, the dynamics of their formation are much the same.
Scientists will now be able to use large computational resources to simulate barchans on Earth and other planets that form over decades or millennia.
