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arXiv · 0911.4267

Aerodynamic Stability and the Growth of Triangular Snow Crystals

K. G. Libbrecht·H. M. Arnold
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Abstract

We describe laboratory-grown snow crystals that exhibit a triangular, plate-like morphology, and we show that the occurrence of these crystals is much more frequent than one would expect from random growth perturbations of the more-typical hexagonal forms. We then describe an aerodynamic model that explains the formation of these crystals. A single growth perturbation on one facet of a hexagonal plate leads to air flow around the crystal that promotes the growth of alternating facets. Aerodynamic effects thus produce a weak growth instability that can cause hexagonal plates to develop into triangular plates. This mechanism solves a very old puzzle, as observers have been documenting the unexplained appearance of triangular snow crystals in nature for nearly two centuries.

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K. G. Libbrecht, H. M. Arnold. 2009-11-22. Aerodynamic Stability and the Growth of Triangular Snow Crystals. https://arxiv.org/abs/0911.4267

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