William Blake, an English poet, is credited with encouraging readers to “see the world in a grain of sand.” Researchers from the University of Campinas in Brazil and the University of California, Los Angeles, have been investigating the “granular” dynamics of how crescent-shaped sand dunes are generated in Physics of Fluids, published by AIP Publishing.
The formations are called barchans, and they can range in size and location from finger-length sand dunes on the ocean floor to stadium-sized dunes in Earth’s deserts to kilometer-long dunes on Mars.
However, there has been a noticeable absence of grain-scale calculations of the development and evolution of barchan dunes up to this point.
Since these dunes may naturally take years to build on Earth or thousands of years to grow on Mars, numerical simulations have traditionally been carried out at huge scales over the past few decades, according to co-author Erick Franklin. “It was nearly hard to track each grain using computations. “Our findings demonstrate how to perform computations that simultaneously address the morphology of barchans, the motion of the grains, and specifics of the fluid flow that affect the forces on each grain.”
Franklin and his colleagues performed simulations using a CFD-DEM (computational fluid dynamics/discrete element technique) strategy by applying the equations of motion to every grain in a pile that was being distorted by a fluid flow.
“By thoroughly simulating tiny dunes in aquatic environments and comparing the results to tests, we investigated the many parameters involved in the numerical computations.” “We displayed the ranges of numbers needed to calculate barchan dunes accurately, all the way down to the grain scale,” Franklin remarked. “This study helps to pave the way for future research into the transmission of forces within dunes and grain mobility, as well as for scaling up the subject so that larger dunes can now be explored using high computer power.”
Although the time and length scales of Martian and terrestrial barchans affected by wind are far larger than those of aquatic examples, which happen in a matter of minutes and centimeters, they do share many of the same dynamics.
With our findings, study teams can now use powerful computers to mimic barchans that occur in other places over centuries or millennia, according to Franklin. Geophysicists, hydrologists, climate scientists, and engineers should be interested in this because it will help anticipate the future of barchan fields on Earth and Mars and give a history of those fields.
