Unblowing bubbles

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The model

Surface tension squeezes air out of a soap bubble through a straw. The model combines air inertia and viscous resistance to predict how the bubble shrinks. Changing the straw length lets you compare how resistance affects its lifetime.

The bubble is treated as spherical, with flow adjusting as it shrinks. This approximation breaks down when the bubble becomes comparable in size to the straw opening, so the final collapse is a theoretical extrapolation. Film colors are illustrative.

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Switch to 3D to orbit · Dimensions in metresΔp = 4σ/R · Inertia + viscosity