Bulletin of the American Physical Society
69th Annual Meeting of the APS Division of Fluid Dynamics
Volume 61, Number 20
Sunday–Tuesday, November 20–22, 2016; Portland, Oregon
Session E16: Drops: Solidification |
Hide Abstracts |
Chair: Detlef Lohse, University of Twente Room: D133/134 |
Sunday, November 20, 2016 5:37PM - 5:50PM |
E16.00001: Dynamics of ice drop explosions in supercooled clouds Detlef Lohse, Sander Wildeman, Sebastian Sterl, Chao Sun The rate at which ice particles are produced in the cold top of natural clouds is crucial in predicting whether a cloud will finally develop precipitation. It has been speculated that ice particles could multiply through freezing and subsequent bursting of supercooled cloud droplets. Here we present high-speed footage of cracking and explosive bursting of spherical water droplets that freeze radially inwards under carefully controlled conditions. We model the processes of freezing, the stress build up in the ice shell, and the fast dynamics following the crack formation. This allows us to predict the time it takes for a freezing droplet to explode and the energy released in this event as a function of the size of the droplet and the temperature of the surroundings. Both predictions are in good agreement with our experiments. The models also predict a minimum droplet radius of approximately $50\mu m$ below which ice explosions are unlikely to occur. This finding has direct consequences in the modeling of cloud microphysics, as the droplet sizes in clouds generally fall in this critical range. Furthermore, we identify several mechanisms, besides the final explosion, by which a freezing drop can shed ice particles. This is important for the formation of ice nucleation avalanches. [Preview Abstract] |
Sunday, November 20, 2016 5:50PM - 6:03PM |
E16.00002: Dueling Mechanisms for Dry Zones around Frozen Droplets Caitlin Bisbano, Saurabh Nath, Jonathan Boreyko Ice acts as a local humidity sink, due to its depressed saturation pressure relative to that of supercooled water. Hygroscopic chemicals typically exhibit annular dry zones of inhibited condensation; however, dry zones do not tend to form around ice because of inter-droplet frost growth to nearby liquid droplets that have already condensed on the chilled surface. Here, we use a humidity chamber with an embedded Peltier stage to initially suppress the growth of condensation on a chilled surface containing a single frozen droplet, in order to characterize the dry zone around ice for the first time. The length of the dry zone was observed to vary by at least two orders of magnitude as a function of surface temperature, ambient humidity, and the size of the frozen droplet. The surface temperature and ambient humidity govern the magnitudes of the in-plane and out-of-plane gradients in vapor pressure, while the size of the frozen droplet effects the local thickness of the concentration boundary layer. We develop an analytical model that reveals two different types of dry zones are possible: one in which nucleation is inhibited and one where the net growth of condensate is inhibited. Finally, a phase map was developed to predict the parameter space in which nucleation dry zones versus flux dry zones are dominant. [Preview Abstract] |
Sunday, November 20, 2016 6:03PM - 6:16PM |
E16.00003: Frozen Impacted Drop: from Fragmentation to Hierarchical Crack Patterns Thomas Séon, Elisabeth Ghabache, Christophe Josserand We investigate experimentally the quenching of a liquid pancake, obtained through the impact of a water drop on a cold solid substrate (0$^\circ$C to -60$^\circ$C). We show that, below a certain substrate temperature, fractures appear on the frozen pancake and the crack patterns change from a 2D fragmentation regime to a hierarchical fracture regime as the thermal shock increases. The different regimes are discussed and the transition temperatures are estimated through classical fracture scaling arguments. Finally, a phase diagram presents how these regimes can be controlled by the drop impact parameters. [Preview Abstract] |
Sunday, November 20, 2016 6:16PM - 6:29PM |
E16.00004: Scaling Laws for Inter-droplet Ice Bridging Saurabh Nath, Farzad Ahmadi, Jonathan Boreyko In this work, we study the dynamics of an ice bridge growing from a frozen droplet towards its neighboring supercooled liquid droplet. Experiments were done on a Peltier stage inside a humidity chamber with deposited or condensed droplets where the substrate temperature and ambient humidity could be controlled. Following a quasi-steady diffusion-driven model, we develop scaling laws to show how the growth rate depends on the substrate temperature, droplet sizes and inter-droplet distances over and above other environmental parameters such as air temperature and humidity. The growth rate as well as the success or failure of an ice bridge to connect to its neighboring liquid droplet depend on a nondimensional number called the separation parameter S$^{\mathrm{\ast }}$, defined as the ratio of the initial inter-droplet spacing to the diameter of the evaporating liquid droplet. It is shown that the maximum value of S$^{\mathrm{\ast }}$ for connection scales as 1 as long as frozen drop is larger than the liquid droplet. For the converse case of a larger water drop, there are at least three separate regimes of critical S$^{\mathrm{\ast }}$, depending on whether the water drop is a puddle, a spherical cap or if the frozen drop is a puddle. [Preview Abstract] |
Sunday, November 20, 2016 6:29PM - 6:42PM |
E16.00005: Contact line arrest in solidifying spreading drops Rielle de Ruiter, Pierre Colinet, Jacco Snoeijer, Hanneke Gelderblom When does a drop, deposited on a cold substrate, stop spreading? Despite the practical relevance of this question, for example in airplane icing and 3D metal printing, the exact mechanism of arrest in solidifying spreading drops has not yet been unraveled. Here, we consider the spreading and arrest of hexadecane drops of constant volume on two smooth wettable substrates; copper with a high thermal conductivity and glass with a low thermal conductivity. We record the spreading radius and contact angle in time for a range of substrate temperatures. We show that our measurements on both copper and glass are well explained by a contact line arrest condition based on crystallization kinetics, which takes into account the effect of kinetic undercooling and the thermal conductivity of the substrate. [Preview Abstract] |
Sunday, November 20, 2016 6:42PM - 6:55PM |
E16.00006: Interface solidification of impinging metal drops Jolet de Ruiter, Dan Soto, Kripa Varanasi Molten metal droplet deposition is important in manufacturing techniques such as spray deposition and metal inkjet printing. Key parameters are the final splat morphology and its adhesion to the base substrate. How to control these parameters is still poorly understood, since droplet deformation, cooling and solidification happen simultaneously. Here, we studied the contact patch formed between the metal drop and the base substrate, varying the thermal properties and the initial temperature of the substrate, and the initial temperature of the drop. We identify various scenarios for interface solidification, including smooth liquid-spread contact patches, entrapment of air pockets, and transient re-melting of the interface. The transitions between various scenarios can be rationalized from the interfacial temperature estimated by heat conduction, and taking into account the flow of liquid metal. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700