Kaye effect

Settled in 2006 by Michel Versluis, Cor Blom, Devaraj van der Meer, Ko van der Weele, Detlef Lohse (University of Twente).

Engineer Alan Kaye first described the effect in a 1963 Nature note, 'A Bouncing Liquid Stream,' after noticing a poured jet of a viscoelastic polymer solution periodically leap sideways off its own landing pool. It remained a curiosity, reproduced mainly with obscure lab fluids, until a Twente group led by Detlef Lohse showed in 2006 that ordinary shampoo and other shear-thinning (but not necessarily elastic) household liquids display a stable, directed version of the effect, and that a model based purely on shear-thinning viscosity reproduces the leap. This settled the long debate over whether elasticity was essential to the phenomenon.

A stream of shampoo apparently defying gravity turns out to be explainable with nothing more exotic than viscosity that changes with shear rate.

Explanations that circulated

• Early accounts attributed the leap primarily to the liquid's elasticity (viscoelastic memory); the 2006 Twente study showed the effect is reproduced by a simple model using only shear-thinning viscosity, with elasticity playing essentially no role.

References

• Leaping shampoo and the stable Kaye effect, M. Versluis, C. Blom, D. van der Meer, K. van der Weele, D. Lohse, Journal of Statistical Mechanics: Theory and Experiment, 2006
• A Bouncing Liquid Stream, A. Kaye, Nature, 1963