Self-propelled swimming and propulsive performance of bio-inspired pitching panels*

Swimming animals using oscillatory propulsive mechanisms propel themselves through the water using either a caudal fin or a fluke located at the rear of their body. The propulsive appendages of swimming animals display a wide diversity in planform, including those with different trailing edge shapes. The current work expands upon prior experimental work on the time-averaged performance of bio-inspired pitching propulsors as measured in fixed velocity water tunnel experiments. Rather than using a fixed velocity free stream flow and pure pitching kinematics, the current work investigates mean propulsive performance using experiments conducted at self-propelled swimming speeds for combined pitching and heaving motions. Trailing edge shape and kinematic parameters are varied for a series of bio-inspired panels with a nominally trapezoidal planform. In total, five unique panel geometries, each with a different trailing edge shape, were actuated with multiple motion profiles until the resultant self-propelled swimming speed was determined. The measured self-propelled swimming results are discussed in the context of changes to planform shape and kinematics. Prior work on the same panel geometries at fixed swimming velocity are compared and contrasted to the findings measured at self-propelled swimming speeds. The current work also focuses on the implications of these findings on the design of bio-inspired vehicles relying on novel propulsive mechanisms and the effects that propulsor geometry and kinematics may have on animals swimming at constant velocity.