Numerical study of hub taper angle on podded propeller performance

Presently, the majority of podded propulsion systems are of the pulling type, because this type provides better hydrodynamic efficiency than the pushing type. There are several possible explanations for the better overall performance of a puller-type podded propulsor. One is related to the difference in hub taper angle. Puller and pusher propellers have opposite hub taper angles, hence different hub and blade root shape. These differences cause changes in the flow condition and possibly influence the overall performance. The current study focuses on the variation in performance of pusher and puller propellers with the same design of blade sections, but different hub taper angles. A hyperboloidal low-order source-doublet steady/unsteady time domain panel method code, PROPELLA, was modified and used to evaluate effects of hub taper angle on the open water propulsive performance of some fixed-pitch screw propellers used in podded propulsion systems. Major findings include good agreement between predictions using the modified code and measurements, significant effects of hub taper angle on propulsive performance of tapered hub propellers, and noticeable effects of hub taper angle on sectional pressure distributions of tapered hub propeller blades.