bubbles!

I'm taking a heat transfer and phase change class, and we talk a lot about interfaces and surfaces, and bubbles! It turns out the shape of a bubble can be approximated pretty well as a function of the density and surface tension of the bubble liquid, the density of the medium it's in, and the curvature at the top of the bubble. With those, you can plot the entire shape of bubble!


For bubbles sitting on a surface there's also something called the contact angle (theta), which is different for each combination of liquid+surface, and how pure the liquid is and how clean the surface is blah blah. It's basically the interior angle the liquid drop forms with the surface, and it can go from almost 0 (the liquid spreads out on the surface) to almost 180 (the liquid balls up on the surface, but isn't quite spherical because gravity squishes it a bit). For example, the same bubble, but with a contact angle of 130 with the surface:


It's the same shape as the full bubble, just cut off when the interior angle reaches 130. For a contact angle of 40, you get:

Anyways, I thought that was pretty cool.
-jenny.