Megan Leftwich, an assistant professor of mechanical and aerospace engineering at George Washington University, was recently inspired by a trip to the Smithsonian National Zoo. A visit to the sea lion exhibit got how asking questions about the unique way the animals swim through the water. Most fish use an oscillating back-and-forth motion with their caudal fins to propel themselves through the water while mammals tend to use an up-and-down motion.
Sea lions instead use their foreflippers to push themselves through the water. Each clap of their flippers down towards their bellies creates a great amount of thrust where they're able to glide for a while before having to use their flippers again. They also produce hardly any wake.
Leftwich studies fluid dynamics and has been conducting research on topics as varied as the wake dynamics of wind turbines to the fluid dynamics of human childbirth. Seeing how sea lions move with so much force, but little wake piqued her curiosity and led to her launching a study on the animal's propulsion.
After hundreds of hours observing them at the zoo and watching video, the study is now at the second phase. Recreating the famous flipper. The team is developing a robotic flipper that will be able to push through the water the same way the real thing can in order to study how the water reacts around the flipper.
Leftwich and her team created 3D scans of the flipper and are putting the finishing touches on the robotic model. Now for putting it into water and seeing what happens. Leftwich says that the robo-flipper will give them a controllable way to study the fluid dynamics of sea lion swimming that observing real sea lions would never allow thanks to their size and the need for very specialized equipment.
The robo-flipper will hopefully help the team gain insight into how the animal achieves such a powerful thrust with barely traceable wake, information that could lead to far better wind turbines and underwater vehicles that could explore caves, shipwrecks or underwater mines -- anything that requires the stealth and agility of a sea lion.