HYDRODYNAMIC INTERACTIONS IN FISH-LIKE ROBOTIC SWARMS WITH FLEXIBLE PROPULSORS

In this work computational models of Bluebots, bio-inspired swimming robots that demonstrate 3D maneuverability and collective behaviors, are developed. Flexibility is prescribed to the caudal fins (CF) using a virtual skeleton. The hydrodynamic interactions occurring within in-line arrangements of these Bluebots is investigated by altering the flexion angle of the leader Bluebot caudal fin and a balance between optimizing leader Bluebot (LB) performance and follower Bluebot (FB) wake interaction is identified. Compared to the rigid CF baseline, optimal CF flexion for the thrust of LB leads to higher negative pressure within generated vortex structures and narrowing of the thrust jet which impinges along the entire body of the FB. Further increase of the LB flexion creates even stronger negative pressure regions while widening the thrust jet behind the leader. These flow conditions are more favorable for the FB as the accelerated flow only interacts with the anterior of the robot body and the stronger negative pressure supplies stronger anterior suction. The ability of the FB to sense these flow changes is also important, and the pressure sensor data on the FB exhibits differences between the cases. Near the anterior surface, the sensor pressure data provides insight to the varying vortex ring strengths for higher LB CF flexion, meanwhile, such differences are not as obvious when examining probe data further downstream on the FB.