Improving underwater thruster performance through jellyfish biomimicry and 2D jet velocity

Biomimicry has gained much popularity recently in engineering design, taking advantage of natural optimization processes. A new underwater thruster design is inspired by propulsion mechanisms of jellyfish, squid, octopus and other cephalopods. The thruster expels finite jets of water periodically to provide necessary maneuvering forces on underwater vehicles and can be placed completely inside the vehicle body. Since the design is inspired by squid and jellyfish propulsion, this paper will investigate one way in which propulsive thrust is enhanced by these animals. A CFD simulation of a swimming jellyfish is analyzed to determine propulsive performance with respect to jetting kinematics, showing that the shape of the velar opening flaps induce a converging radial velocity in the jet increasing the total jet impulse. A prototype thruster was equipped with a set of nozzles to create both parallel and converging jet flows and it was observed that the converging jet flow produced a propulsive jet with ≈ 70% more impulse than the parallel jet flow.