Hydrodynamic Analysis of Cycloidal Propulsors

A phenomenological description of the flow about, and performance of, cycloidal propulsors is extracted from the available literature. An approximate three-dimensional analysis, employing elements of a lifting-line model and an actuator-disk model, is assembled to predict the hydrodynamic loads on an arbitrary-geometry cycloidal propulsor. Both local blade-oriented and total circumferentially-averaged thrust and torque loads are computed·. Comparisons with experimental data and other analysis procedures show that the numerical implementation is generally adequate for preliminary design. Cavitation-inception properties of the blade sections are determined and an empirical prediction of tip-vortex cavitation inception is included. Noise levels are estimated for operation with extensive cavitation on the blade. Several blade-pitch motions are evaluated and it is found that various forms of modified cycloidal pitch control are advantageous for increased thrust from a given unit with little change in hydrodynamic efficiency or cavitation onset. Suggestions are given for future work.