Unsteady aerodynamic force of tilt ducted fan during transition period

In order to study the unsteady aerodynamic force of the tilt ducted fan powerplant during transition period, a unsteady numerical simulation method based on sliding meshes was used. A disk model based on inner flow field information and blade element theory was utilized to simulate the fan propeller, and the Navier-Stokes (N-S) equations were solved to simulate the process of ducted fan during pulling up. The results demonstrate that the hysteresis properties of unsteady aerodynamic force of the ducted fan are obvious at transition period. The increase of pitch rate of the tilt ducted fan delayes the flow field separation, and increase lift and drag of ducted fan. The aerodynamic performance of the ducted fan is excellent in transition period at low speed. Higher speed and larger angles of attack worsen the aerodynamic performance of ducted fan, and the curve of the pitch moment is in a mess against the transition flight.