Exploding a Bubble

Snapshots from the ignition of the bubble's contents.

In this high-speed video, artist Linden Gledhill ignites a mixture of oxygen and hydrogen contained within a soap bubble. As neat as the video is, I decided to take a closer look at the initial detonation with this animation:

The ignition sequence within the bubble, slowed down further.
The ignition sequence within the bubble, slowed down further.

Even here, it’s hard to appreciate just how fast ignition is; it lasts only a handful of frames, despite filming at 40,000 frames per second. But we can still pick out some very neat physics. The ignition begins with a spike-like jet but immediately forks into three ignition fronts that pierce the soap bubble. You can see the shadowy mist of the bubble bursting as the flame front expands. Watch the background carefully, and you can see a shock wave flying away from that moment of detonation.

Once the soap bubble is gone, the expanding flames begin to wrinkle and deform. Turbulence takes shape, eddying through the flames at a much slower speed than the initial detonation. This is where most of combustion takes place, with turbulence mixing the hydrogen and oxygen together to better enable burning. (Image and video credit: L. Gledhill)

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