Optimization of Flapping Dynamics of Rigid and Flexible Fins

Flexible structures are ubiquitous in natural propulsors. However, the significance of fluid-structure interaction for bio-propulsion is not well understood. The relative performance of rigid and flexible fins has been investigated with an experimental trajectory optimization scheme. In an oil tank facility, a robotic fin controlled via a spherical parallel manipulator (SPM) optimizes kinematics with an automated covariance matrix adaptation evolutionary strategy (CMA-ES). This robot enables exploration of complex 3D trajectories with larger rotations than are available to natural propulsors. Previous work has shown that uniformly flexible fins converge to the same trajectories as stiff fins (with lower efficiencies) when optimized for side-force. The present study aims to compare the dynamics of rigid and flexible propulsors with thrust-optimized trajectories. Subsequent flow field measurements will be obtained using digital particle image velocimetry (DPIV) to directly compare the resulting vortex dynamics.