Flowfields produced by a robotic sea lion foreflipper starting from rest

Area of Science:

• Marine Biology
• Biomechanics
• Fluid Dynamics

Background:

• Sea lions are unique aquatic mammals relying on foreflippers for propulsion.
• Existing research primarily focuses on body-caudal swimming, with limited data on sea lion flipper hydrodynamics.

Purpose of the Study:

• To investigate the fluid dynamics of sea lion foreflipper propulsion.
• To analyze the thrust generation mechanism during the flipper's clapping motion.

Main Methods:

• Utilized particle imaging velocimetry (PIV) to visualize flow patterns.
• Employed a robotic model sea lion flipper, accurately replicating a real flipper's geometry and motion.
• Controlled flipper actuation using a programmable servomotor.

Main Results:

• Observed significant fluid momentum entrainment on the suction side of the flipper during the clapping motion.
• Identified the formation of a shed vortex contributing to downstream momentum and thrust.
• Found that increased rotational velocity enhanced jet velocities but reduced efficiency.

Conclusions:

• Sea lion foreflipper propulsion involves vortex dynamics and fluid entrainment.
• The propulsive mechanism can be optimized for different operational requirements.
• This research provides critical insights into marine mammal locomotion and bio-inspired propulsion systems.