In order to optimize the aerodynamic performance of a contra rotating propeller and study the complex unsteady aerodynamic interactions between two propellers of the contra rotating propeller

the unsteady Reynolds-averaged Navier-Stokes (URANS) numerical simulation method and sliding mesh technique were implemented. The three-dimensional unsteady aerodynamic interaction of a 6×6 contra rotating propeller configurations was calculated

which indicated the variation of aerodynamic performance of the contra rotating propeller. Furthermore

the suggestions for optimizing the aerodynamic layout and operation control method were given. The simulation results showed that the fluctuation of the thrust coefficient and power coefficient of the overall contra rotating propeller was about 1.5% and the fluctuation of the propulsion efficiency was about 0.1% due to the unsteady aerodynamic interference at the cruise Mach number 0.38. There were 12 periodic fluctuations in both the front and aft propellers during one rotation. Because the aft propeller of contra rotating propeller can take advantage of the tangential slipstream energy of the front one

it had much higher propulsion efficiency than that of the front propeller

and the efficiency of the overall rotor can be improved too. In addition

according to the distribution of pressure coefficient and axial velocity

the intensity of unsteady aerodynamic interaction was relatively large at 70% of rotor radius.