Upstream contamination by floating particles is a counterintuitive phenomenon in

fluid dynamics In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in motion ...

. When pouring water from a higher container to a lower one, particles floating in the latter can climb upstream into the upper container. A definitive explanation is still lacking: experimental and computational evidence indicates that the contamination is chiefly driven by

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension (physics), tension is what allows objects with a higher density than water such as razor blades and insects (e.g. Ge ...

gradients, however the phenomenon is also affected by the dynamics of swirling flows that remain to be fully investigated.

Origins

Experimental setup for upstream contamination

The phenomenon was observed in 2008 by the Argentine Sebastian Bianchini during mate tea preparation, while studying physics at the

University of Havana The University of Havana (UH; ) is a public university located in the Vedado district of Havana, the capital of Cuba. Founded on 5 January 1728, the university is the oldest in Cuba, and one of the first to be founded in the Americas. Originall ...

. It rapidly attracted the interest of professor Alejandro Lage-Castellanos, who performed, with Bianchini, a series of controlled experiments. Later on professor Ernesto Altshuler completed the trio in

Havana Havana (; ) is the capital and largest city of Cuba. The heart of La Habana Province, Havana is the country's main port and commercial center.Marangoni effect The Marangoni effect (also called the Gibbs–Marangoni effect) is the mass transfer along an Interface (chemistry), interface between two phases due to a gradient of the surface tension. In the case of temperature dependence, this phenomenon may ...

. This was suggested by two facts: (a) both mate and chalk lowered the surface tension of water, and (b) if an industrial surfactant was added on the upper reservoir, the upstream motion of particles would stop. This interpretation was challenged in 2024 by a claim that, under certain conditions, the phenomenon was found to occur even without the presence of the Marangoni Effect. Particles moved upstream even when the surface tension of the lower fluid container was increased by the addition of

calcium chloride Calcium chloride is an inorganic compound, a Salt (chemistry), salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with cal ...

Confirmation

After a talk by Lage-Castellanos at the First Workshop on Complex Matter Physics in Havana (MarchCOMeeting'2012), professor Troy Shinbrot of

Rutgers University Rutgers University ( ), officially Rutgers, The State University of New Jersey, is a Public university, public land-grant research university consisting of three campuses in New Jersey. Chartered in 1766, Rutgers was originally called Queen's C ...

became interested in the subject. Together with student Theo Siu, Cuban results were confirmed and expanded with new experiments and numerical simulations at Rutgers, which resulted in a joint peer-reviewed paper.

References

Fluid dynamics Physical paradoxes Physical phenomena

External links

* *{{cite web , title=Upstream Contamination by Floating Particles , date=2014 , url=https://www.youtube.com/watch?v=PCKu_mwTTI0 , publisher=YouTube , access-date=2014-10-11 , archive-date=2019-09-01 , archive-url=https://web.archive.org/web/20190901042509/https://www.youtube.com/watch?v=PCKu_mwTTI0&gl=US&hl=en , url-status=live

Origins

Confirmation

See also

References

External links