Characterizing the thrust production of partially-submerged flapping propulsors

Archer fish jumping out of the water to capture prey utilize varying tail stroke kinematics throughout their jump. In this study, we experimentally investigate the propulsive performance of flexible plates breaching the air-water interface inspired by these jumps. Analyzing the performance across a range of stroke kinematics and plate flexibilities at different fixed submergence depths reveals how propulsive dynamics change throughout the course of the jump. We measure net thrust using a load cell and wake patterns using 2D PIV. Additionally, we compare both jumping and forward in-water swimming configurations using the same stroke kinematics to investigate the effects of the free surface on the generated thrusts and wakes. Understanding how propulsive dynamics change when partially-submerged allows us to develop flapping profiles for water exit to maximize quantities such as net thrust generated or efficiency.