70th Annual Meeting of the APS Division of Fluid Dynamics (November 19, 2017 — November 21, 2017)

V0042: Drops from a drop

Authors

• Prasanth Prabhakaran, Max Planck Institute for Dynamics and Self Organization
• Stephan Weiss, Max Planck Institute for Dynamics and Self Organization
• Alexei Krekhov, Max Planck Institute for Dynamics and Self Organization
• Alain Pumir, Ecole Normale Superieure de Lyon
• Eberhard Bodenschatz, Max Planck Institute for Dynamics and Self Organization

DOI: https://doi.org/10.1103/APS.DFD.2017.GFM.V0042

In this video, we show the nucleation of droplets in a moist convection experiment in a binary mixture consisting of pressurized Sulphur Hexaflouride (SF6) and Helium (He). This system mimics the earth's atmosphere with SF6 playing the role of water vapor and, He of all the other dry gases. We find that under appropriate conditions a large cold drop, falling into a region of warmer supersaturated vapor, nucleate many micro-droplets in its thermal wake due to the induced isobaric cooling. Our estimates show that this mechanism is relevant for large raindrops and hailstones falling through a supersaturated atmosphere (https://link.aps.org/doi/10.1103/PhysRevLett.119.128701). This acts as a self-seeding mechanism in the atmosphere without any external agents. This mechanism may have strong consequences for precipitation formation in clouds. The video also shows that under appropriate conditions these droplets form a stable horizontal layer separating the regions of super and sub saturation, similar to a cloud base or an edge.