The front dune creates a turbulence that affects the back dune causing the two dunes to move with the same frequency and shape.
Although it is an inanimate thing, the sand dunes can “communicate” with each other according to the interpretation of scientists. A research team from the University of Cambridge has found that when they induce movement, the dunes interact with and repel neighboring dunes in the lower part of the sand mass.
Using an experimental dune, the researchers observed that two similar dunes would initially move closer to each other, but over time they grew further apart. This interaction is controlled by turbulent swirls from the dunes that have movement, pushing the remaining dunes downstream. The results reported in the journal Physical Review help study the long-term migration of sand dunes, the increase in desertification that can bury infrastructure.
When a sand mass is exposed to wind or water currents, it forms a dune shape and will move downstream. Sand dunes, whether in the desert, riverbed or seabed, rarely form individually but often occur in large groups, forming large clusters known as “dune fields” or “corridors ” sand”. The speed at which a dune moves is inversely proportional to its size: small dunes move faster and larger dunes move slower.
Using high-speed cameras, the researchers were able to track the movement of the dunes. (Photo: Cambridge University).
There are many different theories about how the dunes interact, said Dr. The dunes of different sizes will collide continuously until they form a giant dune, a phenomenon that has not been observed in nature. Another theory is that the dunes can collide and exchange mass, like billiard balls bouncing off each other until they are the same size and move at the same speed.
Dr Nathalie Vriend, who led the study, said that in the past, digital methods were often used to model the behavior of sand dunes. But Vriend and her lab members designed and built a unique test system that allowed them to observe the dune’s behavior. The Cambridge researchers used multiple high-speed cameras to track the flow and movement of individual particles in the dunes.
Two sand dunes begin to move with the same frequency and shape. As the current begins to move over the two dunes, they begin to move. “Since the speed of a dune is related to its height, we expect the two dunes to move at the same speed,” Vriend said. Initially, the front dune moved faster than the back dune, but as the experiment continued, the front dune began to slow down until the two dunes were moving at roughly the same speed.
Observing the flow pattern over the two dunes shows that the flow is deflected by the front dune, creating a vortex on the back dune and pushing it away. The front dunes create turbulence that affects the back dunes. As the experiment continued, the dunes grew further and further apart, until they formed an equilibrium facing each other, 180 degrees apart.
Scientists say the future will study the movement of large-scale and complex sand dunes in the desert. By monitoring dune clusters over long periods of time, it is possible to provide a measure of dune movement to minimize impact.