Research on the unsteady aerodynamic characteristics of cycloidal propeller

A prototype of a cycloidal propulsion vehicle which is developed by Northwestern Polytechnical University is chosen as the research model of this paper. To investigate the unsteady aerodynamics of the cycloidal propeller, numerical analysis is conducted on a two-dimensional simplified cycloidal propeller model. The dual-time method is used for unsteady time marching. The dynamic mesh method of the spring-based smoothing method and the local remeshing method are adopted for dealing with the problem caused by the rigid blade motion and mesh deformation. The instantaneous thrust, blade force and unsteady flow fields of the 4-bladed cycloidal propeller are analyzed, and some conclusions are drawn. The instantaneous thrust periodically fluctuates with azimuth as an approximated sinusoidal curve; the average direction of thrust during one revolution keeps almost constant with the variation of the rotation speed of the cycloidal propeller; the curves of blade normal force and blade tangent force coefficients with varying pitch angles are hysteresis loops, and the blade force is obviously larger when the blade moves upward than when it moves downward; the blade aerodynamics is strongly affected by the strong unsteady interactions between wakes of the blades.