Experiments on the morphology of icicles

TL;DR

This study investigates icicle formation through laboratory experiments, revealing that while some icicles conform to theoretical self-similar shapes, others display irregularities like ripples and branching, influenced by water purity and growth conditions.

Contribution

The paper provides experimental validation and challenges to existing theories on icicle shape formation, highlighting the effects of water type and surface instabilities.

Findings

Self-similar icicle shapes are observed under specific conditions.

Ripple patterns can form and climb during growth.

Pure water icicles tend to be more self-similar.

Abstract

Icicles form when cool water drips from an overhanging support under ambient conditions which are below freezing. Ice growth is controlled by the removal of latent heat, which is transferred into the surrounding air via a thin film of water flowing over the ice surface. We describe laboratory experiments in which icicles were grown under controlled conditions. We used image analysis to probe the evolution of the icicle shape under various conditions. A recent asymptotic theory suggests that, overall, icicles converge to self-similar shapes which are predicted to be attractors. On the other hand, stability theory predicts that the ice-water interface can become unstable to form ripple patterns on the icicle surface. Our experimental results show that the predicted self-similar profile is only found in certain cases, and that icicles can also exhibit unpredicted non-uniformities such as branching near the tip. We find that pure water icicles are more likely to be self-similar than those grown from tap water. Ripples, which are also deviations from the self-similar profile, were observed to climb upward during icicle growth.