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Why do bubbles coalesce?

  1. Apr 7, 2017 #1

    joshmccraney

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    Why do bubbles coalesce? I imagine it has to do with surface tension and pressure. The Young-Laplace equation states a bubbles pressure is inversely proportional to its radii. Higher pressure implies higher potential energy, so maybe bubbles coalesce to form a bigger bubble with bigger radii, and hence smaller pressure and less energy?
     
  2. jcsd
  3. Apr 7, 2017 #2
    The surface tension tries to minimize the surface area. One big bubble has lower surface area than two smaller bubbles.

    When two smaller bubbles touch, there's a seam between them. If a tiny hole develops in the seam, connecting the two bubbles, then you have a narrow choke between the two spheres. In the choke, the radius of curvature is very small, so it is very unstable. The Young-Laplace equation refers to a static situation, but gives the idea that the pressure is instantaneously not equal everywhere. Pressure will quickly equalize, which means the bubble needs to reshape itself into a sphere.
     
  4. Apr 7, 2017 #3

    sophiecentaur

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    All the best (and most reliable) arguments are based on energy. "Good on yer!"
     
  5. Apr 7, 2017 #4

    joshmccraney

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    Since energy is proportional to surface area, this is why surface area is minimized, right?
     
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