Dresden 2020 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 3: Fluid Physics of Turbulence

DY 3.8: Vortrag

Montag, 16. März 2020, 11:45–12:00, ZEU 118

Rayleigh-Taylor Instability in Merging Soap Bubbles — •Patricia Pfeiffer1, Qingyun Zeng2, Beng Hau Tan3, and Claus-Dieter Ohl11Otto von Guericke University Magdeburg, Germany — 2Nanyang Technological University, Singapore — 3MIT Alliance for Research and Technology, Singapore

The coalescence of centimeter-sized soap bubbles is studied using high-speed optical imaging. An interference pattern is observed in the area where the bubbles touch each other shortly before merging. This interference rings suggest that the bubbles are forming a dimple before merging and entrap a tiny volume of air between them. Upon merging a water bridge is formed between both bubbles at the crest of the dimpled region, where the distance between the two bubbles is smallest. The rim of the spreading film accelerates for a brief moment, simulations predict less than 1 *s and expands radially from the point of contact. During that time a Rayleigh-Taylor instability sets in resulting in an instability of the rim front. This instability is mainly visible in the area of the dimple since a higher curvature in that regime induces a higher velocity of the rim. At later times, the rim heals into a circular shape. Depending on the surfactant concentration the entrapment of gas pockets is possible with increasing surfactant concentration. However above the critical micelle concentration no further effect of the surfactant concentration on the instability of the rim is observed.

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