|XXXVII Workshop on Geometric Methods in Physics||1-7.07.2018|
|VII School on Geometry and Physics||25-29.06.2018|
Pointy ice structure of a frozen water droplet
A water droplet placed on a cool plate freezes into a singular pointy structure. The effect is observed because density of the liquid decreases after solidification. Therefore, the volume expands (vertically) and ends up with a pointy ice structure. Previously the phenomenon has been examined with a geometrical model but made assumptions did not give the conical top if we used the liquid-solid density ratio that is typical for water. Therefore, we neglected some simplifications and studied freezing process deeply. We investigated the details about heat transfer, size of a droplet, and formation of ice crystals. Our experimental and theoretical results gave a good agreement with each other. The first observed fact was that, transfer of heat is more intense at the edges thus they freeze first. We also investigated the relation between the size of a droplet and formation of a pointy ice structure. According to Bond number we found the maximum size of a droplet. The limitation of a droplet size was caused by surface tension. It should overcome the weight of the droplet in order to form a droplet and the expansion of the volume was vertical and not radial. (if there was radial expansion, the droplet would not freeze into a pointy ice structure) Finally, we investigated formation of ice crystals from vapor molecules that were moving towards frozen ice drop. Experimental results showed that ice crystals are formed more intensively around the pointy top that is because high diffusion of vapor. All the experiments are compared to the theoretical assumptions and they are in good agreement with each other.
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