“A complete theory of icicle shape, including tip growth, self-similarity and the ripple instability, is currently lacking.”
Prompting professor Stephen W. Morris and Antony Szu-Han Chen from the Department of Physics, at the University of Toronto, Canada to construct ‘An apparatus for the controlled growth of icicles’. The team used their specially designed table-top apparatus in an attempt to grow what they call ‘ideal icicles’:
“The most ideal icicles were found for distilled water and gently stirred air. Icicles grown in still air had a higher probability of forming multiple tips. The latter condition contradicts the assumptions of the self-similarity theory, but nevertheless improves the agreement with it.”
A number of the icicles, however, were found to be non-ideal. Some had branched or even split tips. And some showed signs of rippling – which the team also investigated. For, as sometimes happens, unforeseen experimental side-effects provided opportunities for further study.
“A particularly good sample of ripples was found on a long finger of ice that fortuitously formed when the drain of the refrigerated box froze.”
The paper ‘Experiments on the morphology of icicles’ has just been published in arXiv:1008.1922v1 (note: appropriately suspensive download)