Create Your Own Vortex
What do dolphins, humans and volcanoes have in common? They can all produce toroidal vortices of course! Surprised? Grab some food color and a glass of water to find out how.
- Fill a tall glass to the brim with water and wait for at least 30 seconds. Even though it looks still, water keeps swirling for ages so the longer you wait the better.
HINT: Use an eye-dropper if your food colouring is not the squeeze bottle type.
- Squeeze gently so a drop of food color is dangling from the tip of the bottle. Touch the water surface with the drop.
- Wow! The drop of food color shoots down into the water and almost instantly turns into a tiny little donut!
- Look closely and you’ll see the donut is swirling in on itself as it descends. While it’s moving quickly, the ring is very stable and retains its shape.
- As it descends and slows down, the donut suddenly becomes unstable and breaks up - it's called a vortex breakdown. If your water was still enough, a beautiful inverted crown might form. The tips of the crown are even smaller vortex rings.
Source: Surfing Scientist