Suppose that I have 2 bubbles of different sizes located in a liquid, and assume that both of those bubbles are close to one another. What exactly will happen to both of those bubbles? From a surface tension standpoint, I know that the smaller bubble will have higher pressure gas inside than that larger bubble. So, would the smaller bubble be sucked into the larger bubble? Is there a better way to explain this? I know that, if the bubbles were attached with, say, a nanowire, then the pressure gradient would force the smaller bubble's gas into the larger bubble's, but I'm not sure what happens when they're both separated. Any insight/clarification to my interpretation would be greatly appreciated.
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$\begingroup$ "but I'm not sure what happens when they're both separated" - nothing happens when they're separated... $\endgroup$– lemonCommented Oct 2, 2014 at 17:39
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$\begingroup$ ...........why? What if there's a thin film of liquid between them? $\endgroup$– user108149Commented Oct 2, 2014 at 17:55
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$\begingroup$ Can you define what you mean by: close and separated? $\endgroup$– BMSCommented Oct 2, 2014 at 19:42
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$\begingroup$ is there any type of fluid motion? what type of fluid? what type of bubble? are we talking about gas bubbles from you in a bathtub or bubbles in a bubble chamber? there is too many variables to give a simple "yes or no" answer to your question… if you r talking about "forever" suspended bubbles nothing should happen, but i have been wrong before $\endgroup$– user60226Commented Oct 2, 2014 at 21:56
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$\begingroup$ Thanks for the response. In this case, I'm considering gas bubbles in an infinite chamber of liquid. By close, I mean that the distance between each bubble's interface is less than each bubble's respective radius but great enough such that they don't overlap at t=0. $\endgroup$– user108149Commented Oct 3, 2014 at 0:48
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2 Answers
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Beautiful article (great graphics - not sure if they are photos or GCI) at http://math.berkeley.edu/~hutching/pub/bubbles.html - not sure if this addresses "your" kind of bubbles, but worth a look anyway. In general surface tension prevents bubbles from becoming a single larger bubble as there is an intermediate phase when the surface would have to be bigger. Instead they will try to share an interface (surface smaller) and that interface will be curved depending on their relative sizes (the smaller bubble is stronger and pushes the interface to the larger bubble). See the math in linked papers at the above link.
Preview from the above:
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$\begingroup$ Very interesting (and well-done) graphics here; thanks for the link. $\endgroup$ Commented Oct 3, 2014 at 0:50
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Alright, so here's how I'm thinking about the scenario now. I'd appreciate any comments/suggestions on my logic here. If the bubbles are close, density gradients in each bubble will cause some of the gas to diffuse out into the liquid, and, since the small bubble has a larger pressure, the concentration outside of the smaller bubble will be higher than that outside of the larger bubble. Thus, this concentration difference will cause the gas to diffuse into the larger bubble, and, eventually, the small bubble will be completely "consumed" by the larger bubble. Does that sound logical?