Improved hydrodynamic performance of a collective and cyclic pitch propeller by numerical evaluation of the blade design

The collective and cyclic pitch propeller (CCPP) is a novel concept designed to propel and manoeuvre autonomous underwater vehicles (AUVs). Collective pitch control governs the generated thrust, while through cyclic pitch control a manoeuvring force/side-force is generated. Recent work concluded that new solutions are needed to achieve large side-forces without compromising the observed phase shift. In this paper, increasing the blade surface area is rationalised as the most effective pathway to achieve improved CCPP performance. A three-dimensional numerical RANS-based periodic numerical model was used to evaluate three alternative blade designs. Clear performance improvements were realised by the new blade design, manifested in the ability to generate larger side-forces, both absolute and relative based on the actual surface area, at much smaller phase shifts. A performance improvement relation was established, stating that optimal improvement is realised by increasing both the blade's surface area and aspect ratio. At higher aspect ratios, the side-force is produced in a more efficient manner, both from a general force behaviour and a side-force force generation perspective. Finally, an important note was made regarding the future introduction of blade twist in order to address an observed effect on the ‘neutral’ pitch angle.