Inside or outside, we encounter a lot of fluid dynamics every day. Here are some examples you might have noticed, especially on a rainy day:
After a drop falls into a pool, there’s a column-like jet that pops up after it and sometimes ejects another small drop. This is known to fluid dynamicists as a Worthington jet, but really it’s something we all see regularly, especially if you watch rain falling onto puddles or look really closely at your carbonated drink.
Like the Worthington jet, crown splashes often follow a drop’s impact into another liquid. But they can also show up when slicing or stomping through puddles!
Free Surface Dynamics
Anytime you have a body of water in contact with a body of air, fluid dynamicists call that a free surface. How the interface between the two fluids shifts and transforms is fascinating and complicated. Waterfalls are a great example of this, but so are ocean waves or even the ripples from tossing a rock into a pond.
Water-repellent surfaces are called hydrophobic. Water will bead up on the surface and roll off easily. While many manmade surfaces are hydrophobic, like the teflon in your skillet, so are many natural surfaces. Many leaves are hydrophobic because plants want that water to fall to the ground where their roots can soak it up. Keep an eye out as you wash different vegetables and fruits and see which ones are hydrophobic!