Flow Structures Developed by Bio-Inspired Robotic Sea Lion Flippers of Varied Effective Flexibility

Sea lions swim using a combination of both lift and drag based propulsion within their clap-like motion. Previous research has analyzed the flow structures that arose from a single robotic flipper model at varied constant angular velocities through a simulated clapping motion. This enriched our understanding of sea lion swimming and revealed that the predominant flow structure is a thrust-generating vortex. The vortex forms at the dorsal side of the flipper and grows in size until the flipper comes into contact with the flat plate, which represents the sea lion’s body, and then convects in the opposite direction of the sea lion’s forward motion producing forward thrust. Separation effects began occurring at high angular velocities which led to the question of whether these effects were being produced by angular velocity, flexibility, or a coupling of the two. Our research in this analysis investigates three robotic flipper models of varied effective flexibility to visualize the resulting flow structures. We hope to understand the role of flexibility in sea lion propulsion and how it plays into the development of the separation effects we witnessed in previous experiments. Further, we aim to develop a non-dimensional relationship between the flow structures produced by flippers of varied flexibility and angular velocity.