Regensburg 2019 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 18: Fluid physics and turbulence

DY 18.7: Vortrag

Dienstag, 2. April 2019, 12:00–12:15, H20

Drop dynamic due to condensation and evaporation in a thin Rayleigh-Bénard cell — •Stephan Weiss¹, Prasanth Prabhakaran^1,2, Alexei Krekhov¹, and Eberhard Bodenschatz^1,3 — ¹Max Planck Institute f. Dynamics and Self-Organisation, Göttingen — ²Michigan Tech, Houghton, MI, USA — ³Georg-August University, Göttingen

We report on condensation phenomena in a thin horizontal cell, heated from below and cooled from above, i.e., the well known Rayleigh-Bénard setup. We use Sulphur Hexaflouride (SF₆) as the working fluid with the pressure and temperatures of the plates set such that the bottom plate is above and the top plate below the liquid-vapor transition temperature of SF₆. As a result liquid condenses at the top plate forming a thin layer. This layer undergoes a Rayleigh-Taylor like instability, resulting in the formation of drops that arrange themselves into a hexagonal pattern. At sufficient strong heating from below, the drops are stable and are prevented from touching the bottom plate due to pressure caused by evaporation of the liquid at the bottom of the drops, similar to levitating Leidenfrost drops. When the amount of liquid in the cell is increased in the experiment, e.g., by increasing the pressure, the drops increase in size and form larger domains - puddles. Above a critical size, these puddles undergo another instability leading to the formation of wholes (chimneys) inside the liquid domain. The larger the liquid domain, the more such chimneys occur.