Which swim stroke is fastest?
Vocabulary fluid dynamics, laminar flow, turbulence, streamlined, surface tension, propulsion, surface area
To propel themselves through the water, swimmers use different strokes to control drag and lift. But which stroke is the fastest? Some experts have pinpointed the fish kick — a version of the dolphin kick — as the speediest swimming style. Swim coach and engineer Rick Madge dips into the fluid dynamics behind these strokes.
Questions for Students
- Before listening, make a prediction. Which organism is faster: the bottlenose dolphin or the bluefin tuna?
- Both swim strokes were inspired by their real counterparts, the bottlenose dolphin and the bluefin tuna. Based on the discussion, which organism is faster? Justify your decision.
- What is the fundamental difference between the dolphin kick and the fish kick?
- More surface area on a swimmer’s hands helps them pull more water with each stroke. Come up with a way to figure out the surface area of a hand. Use your measurement strategy to figure out who has the largest flipper in your group.
- Think of Rick Madge’s description of a swimmer cutting through the water paired with the undulations of the body. Create a diagram that shows a swimmer optimizing laminar flow. What do you think the shape of the flow around your swimmer looks like? Hint: Think of the car.
- One difference between the fish kick and dolphin kick is their vortices. For a simple introduction to vortices and fluid dynamics, study and build vortex cannons.
- Research more about the fish kick and the dolphin kick. Have students look at tape from the Rio 2016 Summer Olympics to see where and in which races swimmers used the two strokes. Discuss why more swimmers do not use the fish kick if it is indeed faster than the dolphin kick. Kick your research off here, here, and here.