On the basis of dynamic patched grid technology

numerical simulations were implemented on an isolated single-rotating propeller (SRP) configuration by means of solving three-dimensional unsteady Reynolds averaged Navier-Stokes (RANS) equations

and the numerical results were verified by wind tunnel test

showing good agreements with the experimental data. Subsequently

emphasis was placed on investigation of the unsteady flowfield characteristics and aerodynamic interactions of contra-rotating propellers (CRP) configuration. The results showed that the unsteady RANS approach allow for a detailed analysis of the developing characters of the slipstream flowfield and aerodynamic interactions between the two propellers. The main reason of the aerodynamic interactions lied in the mutual effects of the blade tip vortices generated by the front and aft propellers

and the aft propeller reduced the strength of the blade tip vortices of the front propeller. Aerodynamic interactions could lead to the periodic oscillations of the aerodynamic forces

and the frequency of the oscillations was linked to the blade numbers. The 6×6 CRP configuration had 12 aerodynamic oscillations in one full rotation. The freestream could be accelerated twice when passing through the CRP

therefore compared with SRP

the thrust coefficient and power coefficient of CRP almost would be doubled in the same working conditions

meanwhile the efficiency would increase by approximately 1.5%.