Hydrodynamic efficiency improvement of the High Skew Propeller for the underwater vehicle under surface and submerged conditions

Abstract

An algorithm based on the Boundary Element Method (BEM) is presented for designing the High Skew Propeller (HSP) used in an Underwater Vehicle (UV). Since UVs operate under two different kinds of working conditions (i.e. surface and submerged conditions), the design of such a propeller is an unwieldy task. This is mainly due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different. Therefore, some factors are necessary for the design of the optimum propeller to utilize the power under the mentioned conditions. The design objectives of the optimum propeller are to obtain the highest possible thrust and efficiency with the minimum torque. For the current UV, the main dimensions of the propeller are predicted based on the given required thrust and the defined operating conditions. These dimensions (number of blades, pitch, diameter, expanded area ratio, thickness and camber) are determined through iterative procedure. Because the propeller operates at the stern of the UV where the inflow velocity to the propeller is non-uniform, a 5-blade HSP is preferred for running the UV. Finally, the propeller is designed based on the numerical calculations to acquire the improved hydrodynamic efficiency.