Dynamics of supercooled droplets: Impacts, jets, explosions and more

Sterl, Sebastian (2015) Dynamics of supercooled droplets: Impacts, jets, explosions and more.

Abstract:When liquids are cooled below their freezing point without freezing, they are called \supercooled". This counter-intuitive process occurs when an energy barrier exists for creating a nucleus of frozen substance in the liquid. A common occurrence of supercooled liquids is in the form of supercooled water droplets constituting atmospheric clouds at medium and high altitudes, and a common mechanism that causes such droplets to freeze is the presence of aerosols that serve as nucleation points. It is of high importance to our knowledge of cloud formation and the role of aerosols and ice clouds in the global climate system to understand the ways in which supercooled droplets behave, and the mechanisms by which they can freeze. Furthermore, it is highly relevant to the aircraft industry, since supercooled droplets impacting on airplane wings are one of the prime causes of aircraft icing. In this thesis, we present experimental and numerical results on the freezing processes of supercooled droplets. We have used di�erent experimental techniques to create supercooled macro- as well as microdrops, and performed experiments to vary their temperature and the in uence of this temperature on a number of their properties. We have compared the characteristics of impacting supercooled droplets with those of non-supercooled droplets, and discovered the potential of using supercooled droplets for three-dimensional printing applications. Furthermore, we have used highspeed imaging to record the actual freezing process of supercooled droplets and infer the spatial and temporal scales involved herein, and shown how the freezing can cause droplets to explode. We have also constructed physical models to explain the dynamics of both the freezing process and of the explosion process.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
Link to this item:http://purl.utwente.nl/essays/67368
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