Numerical analysis of propulsion performance of the Archimedean screw under mooring conditions

The Archimedean screw is a specialized propulsion device capable of adapting to various terrain conditions. However, the effect of its geometric parameters on underwater propulsion performance has not been extensively studied. In this paper, the propulsion performance of the Archimedean screw under mooring conditions is analyzed using the CFD tool. The study considers the pitch, blade height, blade thickness, and number of helical blades as key geometric parameters, which are analyzed in dimensionless form. Hydrodynamic characteristics and energy loss are used as performance indicators. The hydrodynamic characteristics integrate thrust, torque, and radial force, while energy loss is analyzed using entropy production theory. The average error between the numerical results and experimental thrust curves is 11.4%, validating the reliability of the numerical method. The results indicate that the hydrodynamic characteristics analysis can determine optimal geometric parameters. Specifically, the pitch should be approximately half of the blade length, the number of helical blades should be 2 or 3, and the blade height and thickness should be maximized and minimized, respectively. Entropy production is mainly attributed to unsteady flow, concentrated in the wake region and near the helical blades. Double helical blades exhibit lower energy loss. This study provides a theoretical basis for the design and application of the Archimedean screw.