Hydrodynamics of jet-flapping combinatorial propulsion in a squid-like swimmer: A study on different coordination modes

This study numerically investigates the hydrodynamic performance of a squid-inspired jet-fin combinatorial propulsion system. This squid-like model integrates mantle motion and fin deformation, using dynamic mesh technology to achieve periodic deformation of the mantle and fins. The study compares hydrodynamic differences between various coordination modes under different Reynolds numbers, with a focus on the distinctions between jet propulsion and fin flapping in thrust generation, energy utilization, and vortex structure formation. The results show that at low Reynolds numbers, the continuous movement mode of the mantle and fins yields larger thrust and propulsion efficiency compared to the intermittent mode, while at high Reynolds numbers, the intermittent fin flapping mode reduces drag and results in higher overall propulsion efficiency. Jet propulsion by the mantle demonstrates significant advantages in terms of high thrust and concentrated momentum, while fin flapping excels in efficient low-speed swimming. Additionally, the mantle jet exhibits high propulsion efficiency during contraction, as the vortex ring structure generated by jetting provides significant advantages in kinetic energy utilization and strength retention. This work offers a comprehensive understanding of the complex dynamics in squid-inspired combinatorial propulsion and may provide valuable insights for the design of efficient bio-inspired underwater vehicles.