Gloerfeld, Mark Gideon (2022)
Hydrodynamics of Supercooled Drops Encountering Solidification at Various Moments of Impact.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00022996
Dissertation, Erstveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
Icing of surfaces is a hazard to numerous technical applications like aircraft, wind turbines, ships and power lines exposed to cold environments. Ice accretion on crucial parts can lead to significant decrease in efficiency, unpredictable limitation of function or complete failure. Particularly threatening icing scenarios often involve the impact of supercooled large water drops. Being in an initially meta-stable liquid state, their solidification exhibits a dynamic stage involving fast propagation of dendrites in their bulk. The interaction of dendrites with the fluid flow of a drop impact represents a complex problem which is to date not fully understood. This dissertation is devoted to gaining insight into the underlying physics of the impact of a supercooled large drop onto a cold solid surface superimposed by an impinging cold air flow. Focus lies on the onset of solidification at various times of the impact which relates to different stages of an ice layer growing on a surface. For experimental investigations, an icing wind tunnel was designed, built and commissioned in the course of this thesis. It facilitates experiments of single supercooled large drops of different sizes impacting onto solid surfaces with controlled variation of drop temperature, impact velocity and speed of the superimposing air flow. Investigations involve the impact of supercooled liquid drops which develop a corona splash upon impact. The splash extent and remaining fluid on the surface is connected to an existing theoretical model considering the onset of splashing. A superimposed air flow entails a deformation of the drops before impact which is incorporated in the splashing model and also in a semi-empirical approach, aiming for estimation of the maximum spreading diameter. Moreover, the impact of drops on a flat ice surface is investigated, which is characterized by an early onset of freezing. A vital influence of the fluid supercooling, i.e. the dendrite propagation velocity, is quantified and a modified model for estimation of the spreading diameter of the frozen drop is introduced. Furthermore, the impact of drops experiencing nucleation before impact is investigated. The impact behaviour of such partially frozen drops has never been investigated before and the adaption of a plasticity flow model enabled the quantification of rheological properties of this mixed phase. The findings of this work contribute to a deeper understanding of the physics involved in the fluid flow and its interaction with the dynamic solidification arising upon impact of single supercooled drops. The adapted models, empirical approaches and quantified properties can ultimately be employed to improve numerical models aimed at the prediction of ice accretion on technical surfaces
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2022 | ||||
Autor(en): | Gloerfeld, Mark Gideon | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Hydrodynamics of Supercooled Drops Encountering Solidification at Various Moments of Impact | ||||
Sprache: | Englisch | ||||
Referenten: | Tropea, Prof. Dr. Cameron ; Hussong, Prof. Dr. Jeanette ; Poulikakos, Prof. Dr. Dimos | ||||
Publikationsjahr: | 2022 | ||||
Ort: | Darmstadt | ||||
Kollation: | xxxi, 158 Seiten | ||||
Datum der mündlichen Prüfung: | 26 Oktober 2022 | ||||
DOI: | 10.26083/tuprints-00022996 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/22996 | ||||
Kurzbeschreibung (Abstract): | Icing of surfaces is a hazard to numerous technical applications like aircraft, wind turbines, ships and power lines exposed to cold environments. Ice accretion on crucial parts can lead to significant decrease in efficiency, unpredictable limitation of function or complete failure. Particularly threatening icing scenarios often involve the impact of supercooled large water drops. Being in an initially meta-stable liquid state, their solidification exhibits a dynamic stage involving fast propagation of dendrites in their bulk. The interaction of dendrites with the fluid flow of a drop impact represents a complex problem which is to date not fully understood. This dissertation is devoted to gaining insight into the underlying physics of the impact of a supercooled large drop onto a cold solid surface superimposed by an impinging cold air flow. Focus lies on the onset of solidification at various times of the impact which relates to different stages of an ice layer growing on a surface. For experimental investigations, an icing wind tunnel was designed, built and commissioned in the course of this thesis. It facilitates experiments of single supercooled large drops of different sizes impacting onto solid surfaces with controlled variation of drop temperature, impact velocity and speed of the superimposing air flow. Investigations involve the impact of supercooled liquid drops which develop a corona splash upon impact. The splash extent and remaining fluid on the surface is connected to an existing theoretical model considering the onset of splashing. A superimposed air flow entails a deformation of the drops before impact which is incorporated in the splashing model and also in a semi-empirical approach, aiming for estimation of the maximum spreading diameter. Moreover, the impact of drops on a flat ice surface is investigated, which is characterized by an early onset of freezing. A vital influence of the fluid supercooling, i.e. the dendrite propagation velocity, is quantified and a modified model for estimation of the spreading diameter of the frozen drop is introduced. Furthermore, the impact of drops experiencing nucleation before impact is investigated. The impact behaviour of such partially frozen drops has never been investigated before and the adaption of a plasticity flow model enabled the quantification of rheological properties of this mixed phase. The findings of this work contribute to a deeper understanding of the physics involved in the fluid flow and its interaction with the dynamic solidification arising upon impact of single supercooled drops. The adapted models, empirical approaches and quantified properties can ultimately be employed to improve numerical models aimed at the prediction of ice accretion on technical surfaces |
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Alternatives oder übersetztes Abstract: |
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Freie Schlagworte: | Supercooled Drops, Drop Impact, Solidification | ||||
Status: | Verlagsversion | ||||
URN: | urn:nbn:de:tuda-tuprints-229961 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau | ||||
Fachbereich(e)/-gebiet(e): | 16 Fachbereich Maschinenbau 16 Fachbereich Maschinenbau > Fachgebiet Strömungslehre und Aerodynamik (SLA) 16 Fachbereich Maschinenbau > Fachgebiet Strömungslehre und Aerodynamik (SLA) > Tropfendynamik und Sprays |
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TU-Projekte: | DFG|TRR75|TP C3 TRR 75 | ||||
Hinterlegungsdatum: | 23 Dez 2022 13:38 | ||||
Letzte Änderung: | 28 Dez 2022 07:24 | ||||
PPN: | |||||
Referenten: | Tropea, Prof. Dr. Cameron ; Hussong, Prof. Dr. Jeanette ; Poulikakos, Prof. Dr. Dimos | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 26 Oktober 2022 | ||||
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