Tuna robotics: hydrodynamics of rapid linear accelerations

Area of Science:

• Biomechanical Engineering
• Hydrodynamics
• Animal Locomotion

Background:

• Fish acceleration dynamics are poorly understood.
• Thunniform swimmers typically rely on caudal fin lift-based thrust during steady swimming.
• Lift generation is limited during acceleration from rest due to slow oncoming flows.

Purpose of the Study:

• To investigate alternative thrust-generating mechanisms in thunniform swimmers during acceleration from rest.
• To quantify propulsion dynamics using a robotic fish model.

Main Methods:

• Utilized a robotic yellowfin tuna-inspired platform (Tunabot Flex).
• Generated controlled linear accelerations from rest.
• Measured electrical power consumption, body kinematics, and fluid flow patterns (particle image velocimetry).
• Computed surface pressures, thrust forces, and mechanical power output along the body.

Main Results:

• The head region generated net drag.
• The posterior body exhibited significant thrust generation.
• Identified a novel propulsion mechanism beyond caudal fin lift.

Conclusions:

• Thunniform swimmers employ additional propulsive mechanisms during acceleration from rest.
• The posterior body plays a crucial role in generating thrust.
• This research offers insights into unsteady locomotion for both fish and bio-inspired robots.