Computational analysis of self-pitching propellers performance in open water

This paper presents a numerical study on self-pitching propellers (SPP) in open water aimed at the prediction of the performance in terms of equilibrium pitch-setting and delivered thrust and torque. Differently from other types of propeller, SPP-blades are able to freely rotate about the pivot axis up to the spindle moment due to the centrifugal forces balances that generated by the hydrodynamic loads. In the attempt to provide a reliable prediction of SPP performance, the emphasis of the work is on propeller hydrodynamics modelling; in detail, the Boundary Element Method (BEM) and Blade Element Momentum Theory (BEMT) are herein proposed as fast and accurate hydrodynamic solvers. Both approaches are widely used in the framework of rotating-blades propulsion but their application to self-pitching propellers is nonstandard. Hence, SPP drawbacks and potentialities are highlighted through comparisons with numerical and experimental available data. The final goal of the paper is to provide some guidelines on the effectiveness and robusteness of BEM/BEMT-hydrodynamics when applied to SPP-blades; this might have practical implications for preliminary design and optimal design process.

► Numerical BEMT and BEM tools are applied to self-pitching propellers in open water.
► Performance at fixed pitch-setting close to design is reasonably predicted by BEMT.
► Spindle moment predictions by BEMT requires a devoted tailoring process.
► BEM results show fair agreement with experiments at fixed and self-pitch conditions.
► Viscous-flow and trailing vorticity modelling are areas of improvement of BEM models.