Article contents
A ratchet trap for Leidenfrost drops
Published online by Cambridge University Press: 27 February 2012
Abstract
The Leidenfrost effect occurs when a drop of liquid (or a sublimating solid) is levitated above a sufficiently hot surface through the action of an insulating vapour layer flowing from its bottom surface. When such a drop is levitated above a surface with parallel, asymmetric sawtooth-shaped ridges it is known to be propelled in a unique direction, or ratcheted, by the interaction of the vapour layer with the surface. Here we exploit this effect to construct a ‘ratchet trap’ for Leidenfrost drops: a surface with concentric circular ridges, each asymmetric in cross-section. A combination of experiment and theory is used to study the dynamics of drops in these traps, whose centre is a stable fixed point. Numerical analysis of the evaporating flows over a ratchet surface suggests new insights into the mechanism of motion rectification that are incorporated into the simplest equations of motion for ratchet-driven motion of a Leidenfrost body; these resemble a central force problem in celestial mechanics with mass loss and drag. A phase-plane analysis of experimental trajectories is used to extract more detailed information about the ratcheting phenomenon. Orbiting drops are found to exhibit substantial deformations; those with large internal angular momentum can even undergo binary fission. Such ratchet traps may thus prove useful in the controlled study of many properties of Leidenfrost drops.
JFM classification
- Type
- Papers
- Information
- Copyright
- Copyright © Cambridge University Press 2012
References
Cousins et al. supplementary movie
Supplemental movie 1: Quasi-one-dimensional orbit of a Leidenfrost drop in a ratchet trap. This high-speed movie shows a drop with very small initial orbital angular momentum executing back and forth motion around the trap centre. The drop exhibits noticeable shape deformations near the turning points of the orbit.
- 75
- Cited by