Questions about bubble behaviour

[Chiefly]

Watching the bubble that formed on top of my Gin and Tonic was interesting.
First I noticed a fine stream of bubbles coming up under a larger surface bubble. The fine stream, about 5-10 per second were just visible.
The surface bubble moved around some 1/4 or 1/2 diameter of the bubble in what seemed random directions.

I assumed this was surface tension from the micro bubbles affecting the big bubble. Fascinating.

Then one instance the bubble moved away by say 10mm or 2 x dia of the bubble. The fine stream of micro bubbles now turned toward the surface bubble in a gentle arc from what appeared to be 20mm below the surface. The stream of micros continued to merge with the bubble until it burst.

By the way it was my first G&T so the mind was clear.

What forces would pull the micros to the bubble even though it was up to 15 or 20mm away from the overhead. I cannot think surface tension can extend underwater so what is the force or attraction involved here?

Thanks

 

[berkeman]

By the way it was my first G&T

I was going to ask about that; thanks for clarifying.

 

[Chiefly]

Don't worry it is a new day, so nearly time to set up today's experiment.
As they say, 'good experiments are repeatable by peers'.

 

[Baluncore]

What forces would pull the micros to the bubble even though it was up to 15 or 20mm away from the overhead. I cannot think surface tension can extend underwater so what is the force or attraction involved here?

I believe you have it backwards. The surface bubble does not control the rising stream of micro-bubbles, the rising stream drives the surface bubble on, or across, the surface.

The bubbles form at depth on a nucleation point, maybe an imperfection, or a grain of sugar, on the surface inside the glass. As the bubble grows, it reaches a point where its buoyancy overcomes surface tension. Bubbles are then released, to rise as a train of similar sized small bubbles, from the one nucleating point. The rising bubbles entrain the surrounding liquid, to form a density convection stream that rises towards the surface, and then spreads out radially at the surface.

Surface bubbles can be held at the centre of the stream on the surface, as small bubbles rise, join, to build a bigger surface bubble. The surface bubble can rotate about a horizontal axis in the surface, as it grows. At some point, like a ball, stable on at the top of a vertical jet, asymmetry in the rising stream can push the surface bubble sideways, where it appears to be followed by the train of bubbles, still rising in the same, now asymmetric, fluid convection cell.

You can study the process by dropping the smallest grain of sugar into a carbonated liquid, that grain will then nucleate and release a train of CO₂ bubbles. Use a large clear glass. Investigate the way that the concentration of juniper oil, used as flavour in the Gin, affects the surface tension, to moderate the size of bubble released, and the way that bubbles merge at the surface.

Does the oil seem to calm your stormy seas, in the late afternoon?
Do you find watching the rising bubbles therapeutic?