title: Exploring the boundary between a siphon and barometer in a hypobaric chamber.
abstract: Siphons have been used since ancient times, but exactly how they work is still a matter of debate. In order to elucidate the modus operandi of a siphon, a 1.5 m high siphon was set up in a hypobaric chamber to explore siphon behaviour in a low-pressure environment. When the pressure in the chamber was reduced to about 0.18 atmospheres, a curious waterfall-like feature appeared downstream from the apex of the siphon. A hypothesis is presented to explain the waterfall phenomenon. When the pressure was reduced further the siphon broke into two columns--in effect becoming two back-to-back barometers. This experiment demonstrates the role of atmospheric pressure in explaining the hydrostatic characteristics of a siphon and the role of molecular cohesion in explaining the hydrodynamic aspects.
authors.affiliation: Department of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4001, Australia.
authors.forename: Stephen
authors.initials: S
authors.lastname: Hughes
authors.affiliation: Paro College of Education, Royal University of Bhutan, Paro, Bhutan and Department of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4001, Australia.
authors.forename: Som
authors.initials: S
authors.lastname: Gurung
references.citation: Am J Physiol. 1992 May;262(5 Pt 2):R725-32
references.pmid: 1590467
references.citation: New Phytol. 2004 Sep;163(3):451-452
references.pmid: 33873751