Unsteady aerodynamics of contra rotating open rotor (CROR) was simulated by solving unsteady Reynolds averaged Navier-Stokes equations based on dynamic patched technology. To analyze the aerodynamic interactions and slipstream flows interactions between the front-rotor and aft-rotor

a 10×10 CROR configuration was adopted and compared with the 10-bladed single rotor. Result shows that

compared with the single rotor

the thrust coefficients and power coefficients of the front-rotor decrease while those of the aft-rotor increase

with 20 periodical oscillations during one rotation period. The spectral analysis of front-rotor and aft-rotor thrust coefficients show that the fluctuations occur at even multiple numbers of blade passing frequency of single rotor

and the amplitude of aft-rotor thrust at twice the blade passing frequency is prominent. Due to the periodical passing of blade tip vortices of front-rotor

the thrust distributions on aft-rotor blade are changed and fluctuate unsteadily. Compared with the single rotor

the axial velocity increases while the cirumferential velocity decreases in the slipstream behind front-rotor. The aft-rotor accelerates the slipstream while recovers swirls.