Impact of arm morphology on the hydrodynamic behavior of a two-arm robotic marine vehicle

Increasing the functionality and efficiency of small underwater marine robotic systems has been a significant challenge, particularly regarding their use in tasks requiring enhanced maneuverability, long-distance travel and delicate underwater manipulation of objects. In this paper, we explore the impact of bio-inspired arm morphology on underwater propulsion, through examination of the generated hydrodynamic forces and the corresponding complex vortical patterns in the wake of a novel two-arm underwater robotic swimmer, inspired by the octopus arm-swimming behavior. We demonstrate for the first time, via detailed modelling and CFD studies, the use of a variety of slender arm morphologies as thrust actuators in a system that can achieve forward propulsion, by the slow opening and rapid closing of these arms ("arm sculling"), while minimizing the lateral excursion of the system. Robotic prototypes, based on such principles, have already been used by our group to observe marine ecosystems, without disturbing them as much as current ROVs. Further applications of such robotic systems could be envisioned in future medical rehabilitation studies.