Freezing singularities in water drops

TL;DR

This study visually demonstrates how water drops freeze into singular shapes on cold surfaces, revealing the development of a sharp tip that influences vapor deposition and crystal growth.

Contribution

It provides a detailed visualization of the freezing process and the formation of a singular tip, highlighting the physical phenomena involved in water solidification.

Findings

A singular tip forms spontaneously during freezing.

The tip acts as a vapor deposition site, promoting ice crystal growth.

The freezing process involves a smooth front followed by a sharp tip formation.

Abstract

In this fluid dynamics video we show how a drop of water freezes into a singular shape when deposited on a cold surface. The process of solidification can be observed very clearly due to the change in refraction when water turns into ice. The drop remains approximately spherical during most of the process, with a freezing front moving upwards and smoothly following the interface. However, at the final stage of freezing, when the last cap of liquid turns into ice, a singular tip develops spontaneously. Interestingly, the sharp tip of the ice drop acts as a preferential site for deposition of water vapour, and a beautiful "tree" of ice crystals develops right at the tip. The tip singularity attracts the vapour in analogy to a sharp lightning rod attracting lightning.