# gst: sand dunes 'communication' via turbulent swirls

<< Even though they are inanimate objects, sand dunes can 'communicate' with each other. A team (..) has found that as they move, sand dunes interact with and repel their downstream neighbours. Using an experimental dune 'racetrack', (they) observed that two identical dunes start out close together, but over time they get further and further apart. This interaction is controlled by turbulent swirls from the upstream dune, which push the downstream dune away.  >>

Sand dunes can 'communicate' with each other. University of Cambridge. 

 Feb 4, 2020.

https://m.phys.org/news/2020-02-sand-dunes.html

Karol A. Bacik, Sean Lovett, et al. Wake Induced Long Range Repulsion of Aqueous Dunes. Phys. Rev. Lett. 124, 054501. Feb 4, 2020.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.054501

Also

keyword 'sand' in Notes

https://inkpi.blogspot.com/search?q=sand

# gst: apropos of turbulences close to a wall, the repetitive structure of a vortex

<< At the boundary where a fluid flows over a fixed structure, a turbulent boundary layer is created where the fluid interacts with the wall, creating eddies in the current. These eddies may seem to be random on first glance, but they actually create distinct patterns, with countless tiny eddies close to the wall; fewer but larger eddies located a little farther out; and even fewer, but still larger, eddies beyond those. >>

<< "We knew that, underlying these very complicated structures, there had to be a very simple pattern. We just didn't know what that pattern was until now," says McKeon, who next plans to dig deeper into the model to quantify just how many eddies should be included to create an accurate representation of the whole. >>

Engineers exploit the repeating structure of turbulence to create a more complete model of the phenomenon. California Institute of Technology. Nov 6, 2019.

https://m.phys.org/news/2019-11-exploit-turbulence-phenomenon.html

Beverley J. McKeon. Self-similar hierarchies and attached eddies. Phys. Rev. Fluids 4, 082601(R). Aug 26, 2019.

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.4.082601