Floating and Falling Flows
Students discover fluid dynamics related to buoyancy through experimentation and optional photography. Using one set of fluids, they make light fluids rise through denser fluids. Using another set, they make dense fluids sink through a lighter fluid. In both cases, they see and record beautiful fluid motion. Activities are also suitable as class demonstrations. The natural beauty of fluid flow opens the door to seeing the beauty of physics in general.
Figure 1. Rising and falling. Green droplet is liquid food coloring in vinegar; red droplet is liquid food coloring in sugar syrup.
Engineers use their knowledge of fluids to invent, repair, reinforce and improve previous inventions that use liquids and gases. When engineers understand fluids, they can help make airplanes, ships, fire truck pumps, fans, water heaters, paper mills, glass factories and soda pop bottling plants. Even understanding the behavior of fluid flow from a cough or sneeze can help engineers design better tissues.
After this activity, students should be able to:
- Describe some aspects of buoyancy-driven flows.
- Understand that gravity, shear force and surface tension can affect fluid flow.
- See that visualizing a fluid flow can both show the physics that are occurring, and be beautiful.