Design of AUV propeller based on a blade element method

Design of a propeller for Florida Atlantic University's Ocean Explorer (OEX) series autonomous underwater vehicle (AUV) is presented. The primary requirement of the design is that the vehicle achieve a steady forward speed of 5 [knots] using a direct-drive motor limited by a torque of 4 [Ed-m] at 1000 rpm. The thrust required to propel the vehicle at steady 5 [knots] was estimated to be approximate to 100 [N]. The estimation takes into account, empirically, the effects of hull-propeller interactions on flow into the propeller and vehicle drag. While an elaborate hydrodynamics analysis is envisaged for the design of AUV propellers in the future, a blade element method is used in the present design. Assuming a functional form of loading curve and radial variation of chord together with the blade-element method, a three-bladed propeller of diameter 34 [cm] and based on NACA 66-221 sections is designed. Sea trials are planned to evaluate the performance of the propeller.