Understanding the Dynamics of Soap Bubble Pinch-off

Courtney Cromartie, Daniel Lathrop, Sonali Shukla

Inspiration for Project

Soap Film Topology Talk with Keith Moffatt

Unfolding a mobius stripSingularities in catenoids

What About a Blown Bubble?

Stages of Pinch-off

Apparatus Design

Experimental Set-up

High-speed video camera2,000 fps, 140 x 160 pixel frame

Pressurized AirDesigned a valve system to control the delivery of air to the nozzle

External Triggering DeviceProvided precision control timing of camera and air burst

Optimizing Bubble Dynamics

Soap Solution60 ml distilled water, 10 ml Dawn

dishwashing liquid, 3 ml glycerol

Careful balance of pressure and air burst length to produce:

SymmetricSingle-pinch off eventsConsistently

Edge Tracing & Image Analysis

z - z0 = (internal wall location) – (location of internal collapse)

Controlling Forces

Proposed that surface tension and kinetic energy of fluid control the process of pinch-off

Dimensional Analysis of force equality uncovers a 2/3’s power law between length and time.

Preliminary Results from 10 Events

Later Stages of Collapse

Early Stages of Collapse

Closing Thoughts

Kinetic Energy and Surface Tension likely play a role in the early stages of pinch-off

A camera with a higher frame rate and better resolution would yield more definitive results close to pinch-off

Special Thanks To:

Daniel Lathrop & Sonali ShuklaUMD TREND ProgramNational Science Foundation