Kaye effect

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A falling stream of shampoo shows the Kaye effect. The Kaye-Effect.jpg
A falling stream of shampoo shows the Kaye effect.

The Kaye effect is a phenomenon observed in some complex liquids which was first described by the British engineer Alan Kaye in 1963. [1]

While pouring one viscous mixture of an organic liquid onto a surface, the surface suddenly spouted an upcoming jet of liquid which merged with the downgoing one.

This phenomenon has since been discovered to be common in many non-Newtonian liquids (liquids with a shear-stress-dependent viscosity or viscoelastic properties). Common household liquids in this category are liquid hand soaps, shampoos and non-drip paint. The effect usually goes unnoticed, however, because it seldom lasts more than about 300 milliseconds. The effect can be sustained by pouring the liquid onto a slanted surface, preventing the outgoing jet from intersecting the downward one (which tends to end the effect).

Whilst it was long thought to occur due to a shear-thinning slip layer, [2] recent studies have shown through high-speed videos [3] and experiments in a vacuum chamber [4] that an extremely thin layer of air (approximately 1000 times thinner than the jet diameter) is entrained, which acts as a lubricant and supports the sliding jet.

The current theory is that viscoelasticity is key. In a jet viscoelastic fluid, a portion of the energy of deformation as the jet falls is recoverable, and this reduces the force required to support the leaping jet, enabling more air to be entrained. [4]

References

  1. Kaye, A. (1963). "A Bouncing Liquid Stream". Nature. 197 (4871): 1001–1002. Bibcode:1963Natur.197.1001K. doi:10.1038/1971001a0. S2CID   4265638.
  2. Versluis, M.; Blom, C.; van der Meer, D.; van der Weele, K.; Lohse, D. (2006). "Leaping shampoo and the stable Kaye effect". Journal of Statistical Mechanics: Theory and Experiment. 2006 (7) P07007. arXiv: physics/0603183 . doi:10.1088/1742-5468/2006/07/P07007. S2CID   119096147.
  3. Lee, S.; Li, E.; Marston, J.; Bonito, A.; Thoroddsen, S. (2013). "Leaping shampoo glides on a lubricating air layer". Physical Review E. 87 (6) 061001. Bibcode:2013PhRvE..87f1001L. doi:10.1103/PhysRevE.87.061001. hdl: 1969.1/185287 . PMID   23848618.
  4. 1 2 King, J.; Lind, S. (2019). "The Kaye effect: New experiments and a mechanistic explanation". Journal of Non-Newtonian Fluid Mechanics. 273 104165. doi: 10.1016/j.jnnfm.2019.104165 .