Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Focus: Droplets (joint session DY/CPP)

CPP 18.5: Vortrag

Montag, 12. März 2018, 16:30–16:45, BH-N 334

Oscillatory wetting under drops impacting on a hot plates — •Kirsten Harth, Michiel A. J. van Limbeek, Chao Sun, Andrea Prosperetti, and Detlef Lohse — Physics of Fluids, Max Planck Center for Complex Fluid Dynamics and University of Twente, The Netherlands

The Leidenfrost phenomenon, where an evaporating drop levitates above a layer of its vapour on sufficiently hot plates is well-known for gently deposited drops. For impacting drops, the additional impact pressure can cause much thinner vapour layers in the nanometer range, and conventional side or bottom view imaging is incapable of detecting substrate contact. Using frustrated total internal reflection (FTIR), three main regimes were distinguished: contact, nucleate boiling at low temperatures (drop spreads in contact with substrate), Leidenfrost (film) boiling without contact and a broad transition regime. Then, the outer parts of the spreading lamella levitate, while the central region of the drop touches the substrate. However, the wetted locations and the drop's partially levitated bottom surface increasingly fluctuate with increasing temperature. Most striking are periodic waves travelling from the lamella tips toward the centre of the wetted region. We analyze and discuss this currently unresolved phenomenon.