Supplementary Material

High-speed visualization of soap bubble blowing and image-processing-based analysis of pinch-off dynamics

John Davidson and Sangjin Ryu*

Department of Mechanical and Materials Engineering University of Nebraska-Lincoln, Lincoln NE 68588, USA

Email: sangjin.ryu@unl.edu

Figure S1. Schematic geometry of a gas bubble or liquid drop (A) prior to pinch-off (t < tpinch-off) and (B) near pinch-off (t tpinch-off). As the fluid thread of initial radius R extends, the minimal radius r decreases, and the time left till pinch-off τ decreases until pinch-off occurs.

Figure S2: Conceptual diagram of determining the soap film tube volume. The tube is approximated as a stack of circular disks of which the thickness (x) is one pixel, and the disk diameter di is determined by the distance between the upper and lower profile as a function of the distance from the soap ring xi. Then, the volume of the soap film tube is approximated by the sum of the disk volume.

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Figure S3: Airflow speed measured at the center of the nozzle (Ue) by the Pitot-static tube.

Movie S1. Image analysis for the minimum neck radius measurement: Result of Figure 2. Movie S2. Image analysis for the minimum neck radius measurement: Result of Figure 3.Movie S3. Soap bubbling video for Ring 3 (2R = 19.1 mm): Video of Figure 5.Movie S4. Soap bubbling video for Ring 1 (2R = 8.4 mm)Movie S5. Soap bubbling video for Ring 2 (2R = 12.7 mm)

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