Abstract: The piston-type synthetic jet propeller represents an emerging underwater propulsion technology, for which enhancing thrust output for the actuator is currently critical challenges. To address these issues, drawing biomimetic inspiration from cephalopods such as the octopus, this paper presents a piston-type synthetic jet propeller actuated by a crank-connecting rod mechanism. An efficiency expression for the propeller is defined by analyzing the force transfer relationship between the piston and the jet, tailored to specific excitation sources and application scenarios. Using numerical simulations, the effects of driving signals and actuator geometric parameters on thrust performance and efficiency are investigated, along with their underlying mechanisms. The results show that when stroke A≥0.02 m, the efficiency curve as a function of frequency f exhibits an extremum. A further increase in A causes this extremum to occur earlier. The crank-connecting rod ratio influences the continuous distribution characteristics of thrust over one cycle: although increasing this parameter enhances thrust, it also reduces efficiency. Both increasing the orifice depth and reducing the orifice diameter help improve the axial proportion of jet velocity, thereby increasing thrust. However, an excessively small orifice diameter restricts the actuator’s ability to exchange fluid with the external environment, leading to a decline in both thrust and efficiency. Further analysis demonstrates that the thrust of the proposed piston-driven propeller exceeds that of the piezoelectric-driven counterpart by 1–2 orders of magnitude. Moreover, under equivalent negative peak thrust conditions, its positive peak thrust reaches 2.12 to 2.35 times that of propellers using the same actuation type.

Key words: Underwater propeller')">Underwater propeller, Piston-type synthetic jet, Fluid-structure interaction, Thrust characteristics, Force transfer efficiency, Jet velocity distribution