The aerodynamic interaction of coaxial rotor during the meeting of blades is most intense in the periodic interaction. In order to explore the characteristics of the flow field interference during the meeting of upper and lower blades of coaxial rotor

a numerical simulation method for aerodynamic interaction based on the unsteady Reynolds averaged Navier-Stokes (RANS) equations was established. Moving overset grid was applied to simulate the motion of the coaxial rotor. The motion of two airfoils with relative horizontal translations in the flow field was simulated to investigate the characteristics of flow field interference at a specific cross section of coaxial rotor. The variation of aerodynamic performance and the characteristics of flow field for the coaxial rotor and two airfoils system were analyzed

and the parameter effects of two airfoils system on the aerodynamic interaction were discussed. Results indicated that the lift increased first and then decreased dramatically during approaching of blades of the coaxial rotor and two airfoils system

and finally became stable. The lift fluctuation amplitude of upper and lower rotors was 30% and 22%

respectively. The aerodynamic interaction between the upper and lower airfoils decreased with the increase of the separation distance

and the lift fluctuation of the upper and lower airfoils changed differently to the variation of separation distance. The amplitude of the lift fluctuation of the two airfoils rose with the relative thickness of airfoil

and the secondary fluctuation occurred. The amplitude and range of the lift fluctuation of the airfoils with smaller relative inflow velocity were larger when there was extra inflow.