Large-eddy simulation of blade-turbulence interaction in a cyclorotor system

Cyclorotor is a propulsion system that has multiple blades rotating around an axis parallel to the blades' spanwise direction, alternately playing roles in both suction (upper) and blowing (lower) sides of the cyclorotor. To investigate how the mechanism of the interactions between the blade-induced turbulence and the cyclorotor's components, such as the blades and the shaft, affect the overall aerodynamic performance of a cyclorotor, large-eddy simulations (LES) are conducted. This study is performed for a cyclorotor comprising six NACA0010 blades that rotate at 800 rpm with a maximum angle of attack of 20°. The results show that the downwash generated by the upper blades of a cyclorotor intensely interacts with the lower blades, reducing some of the thrust generation. This effect peaks at the lower side of the cyclorotor where the angle of attack of the passing blade is the largest and is expected to generate the most thrust. Also, when the shaft is present, it interacts with the downwash generated by the upper blades and alters the trajectory of the downwash towards the lower blades, which increases the overall thrust generation of the blades alone. However, the drag produced by the shaft outperforms the increased thrust by the blades, which consequently generates less total thrust than the cyclorotor without the shaft.