Sand dunes can "communicate" with each other. This conclusion was reached by a group of scientists at the University of Cambridge, which found that as they move, sand dunes interact with each other and even "push" their neighbors downstream.
The results of the study, presented in Physical Review Letters, are key to studying long-term dune migration, which threatens shipping canals, exacerbates desertification and can cause significant damage to infrastructure, mainly highways, which are located in close proximity to sandy terrain.
When a pile of sand is exposed to wind or water, it forms the shape of a dune and begins to move downstream. Sand dunes, whether in deserts, on river beds, or on the seabed, are rarely found singly and usually appear in large groups, forming striking patterns known as dune fields or corridors.
Researchers found out during observations that two identical neighboring dunes first approach each other, but over time they move further and further from each other. This interaction is controlled by turbulent eddies from the rising dune, which push it downstream.
Much of the work on modeling the behavior of sand dunes is done mathematically, but scientists at the Cambridge Laboratory designed and constructed a unique experimental setup that allowed them to observe the long-term behavior of the dunes. The researchers created a circular stream in the installation so that the dunes could be observed for several hours while it rotated, and high-speed cameras allowed them to track the flow of individual particles in the dunes themselves.
“I originally put a few dunes in the rig just to speed up data collection, but we didn't expect to see them interact with each other,” said study leader Karol Bachik, professor in the Department of Applied Mathematics and Theoretical Physics at Cambridge. Two dunes of the same volume and shape were placed in the installation. When the stream of water began to flow across the two dunes, they began to move. Initially, one dune moved faster than the other, but as the experiment continued, its movement began to slow down until the two dunes began to move at almost the same speed.
As the experiment continued, the dunes became farther and farther apart until they formed a kind of equilibrium on opposite sides of the circular stream, remaining 180 degrees apart. The next phase of the study will be to find evidence of large-scale and complex dune migration in deserts using observations and satellite imagery. By tracking accumulations of dunes over long periods of time, phys.org notes, scientists will be able to determine how effective current measures are to divert migratory dunes from infrastructure.