Re: [PSUBS-MAILIST] Bubble question Psubs disscussion

["John R. Farrington" <jrf@austin.ibm.com>]

> Actually , i have a question for those interested in physics under the water
> and mind games.
> he he lets see who guess it right here, Jeffrey you are welcome........
> what would be the shape of an air bubble in the water without the
> hydrodynamic effect (which deforms the bubble because of water flow)
> imagine an air bubble trapped in a container of water, itself going to the
> surface at the speed ascent of an  air bubble. so the only forces exerted on
> the bubble are the water pressure.   water around the bubble is moving with
> the bubble, so there is no flow around the bubble, the container takes the
> hydrodynamic forces.
> Herve


If the bubble is not constrained in any way (like in a balloon), and that
no hydrodynamic forces exist in this theoretical model, I'd think that the
bubble would have to take on an infinitely thin shape of a plane,  (not
an airplane, a geometric plane), with all points at the same depth.  If any
point in the bubble was deeper than another, the pressure on that point would
be greater than anywhere else in the bubble and would be pushed into the bubble.
(The pressure in a gas is uniform - so all points in the bubble must be at
the same pressure (depth)).

So, would it take on the shape of a very thin sheet rising to the surface?


-John

ps.  Interesting how bubbles of different size take on different shapes.  Real
     small ones stay nearly perfectly round (cohesion?), while larger ones
     can take on the shape of a mushroom cap or the shape of a jellyfish.  Others
     are like inverted raindrops.