Numerical analysis of blade-tip vortex effect on turbulence in a cyclorotor system

A cyclorotor is a propulsion system that has multiple blades rotating around an axis parallel to the blades' spanwise direction and generates thrusts by dynamically controlling the angle of attack of each blade. It is capable of instantaneous thrust vectoring in any direction and magnitude. In addition to the benefit of maneuverability, due to its lower blade-tip velocity compared with a conventional propeller, it features lower noise generation. However, few aerodynamic investigations have been conducted through experimental and numerical analyses. In this study, large-eddy simulations (LES) of a cyclorotor are conducted to investigate the effect of the blade-tip vortex on the turbulence generation and consequently the aerodynamic performance of a cyclorotor. Specifically, the results of an LES with an infinite spanwise length by setting the spanwise boundary as periodic and another LES with a finite spanwise length to consider the blade-tip vortex effect are compared. Results show that, when the blades have blade tips, the spanwise inlet towards the center of the cyclorotor induces a significant change in the formation of the turbulence.