Icicles are a common ice formation\, familiar to anyon e who lives in a cold climate. The shape of an icicle emerges from a deli cate dance between solidification\, hydrodynamics and heat transport. Man y\, but not all\, natural icicles are observed to be decorated around the ir circumference by ribs or ripples. These features are presumed to be th e result of a morphological instability in the growth process of the ice. The sides of an icicle are covered by a thin supercooled water film whic h flows down their nearly vertical surface. The wavelength of the ripples \, which is always found to be near 1~cm\, is surprisingly constant\, eve n under diverse growing conditions. A recent detailed study in which hund reds of icicles were grown in controlled laboratory experiments revealed that trace amounts of impurities are required for the formation of the ri pples. Icicles grown from distilled water have no ripples. Ripples appear at a remarkably low concentration of impurity\, becoming me asurable abo ve a concentration of just 10
In this ta lk\, we will discuss our recent experiments in which the concentration an d molecular species of the impurity were varied\, as well as our progress toward a generalized linear stability analysis of the growing ice surfac e\, which includes the effects of impurities. The theory crucially depends on the boundary conditions on the ice-water interface and the possible p resence of a mushy layer near this interface.
Related Links
- http://www.physics.utoronto.ca/Icicl e_Atlas/ - Open source data archive
- http://dx.doi.org/10.1088/1367-2630/15/10/103012 - publica tion \;