To solve the tiltrotor aircrafts complicated flow problems of different speed scales

an unsteady pre-conditioning method and corresponding boundary conditions were developed for simultaneous solution of incompressible and compressible flows. Combined with the unstructured hybrid grid generation technique and the overlapping grid interpolation technique suitable for the complex configuration and large displacement of tiltrotor aircraft

a numerical simulation method for tiltrotor aircraft was presented. On this basis

the validity of the numerical method was verified by hovering case at first

and the principle of preconditioning parameter selection was determined. Then

the wake vortex structure evolution of the hovering configuration for the helicopter mode was investigated

and the effects of “fountain effect” and “ground effect” on the aerodynamic performance of tiltrotor were studied. The results showed that the dissipation of the wake vortex presented different scene in different azimuthal zones. And “ground effect”

coupled with “fountain effect”

suppressed the development of rotor wake. The “ground effect” affected the entire azimuthal zone instead of the zone above the wing

causing a slight increase of 5.26% in the thrust coefficient of the installed rotor relative to the isolated rotor

but the total thrust coefficient of the whole tiltrotor aircraft were only 82.46% of the isolated rotor. The conclusion shows that the preconditioning method is able to simulate the complicated flow field in the hovering configuration of the helicopter model well. Aerodynamic interaction has a significant impact on the overall aerodynamic performance of the tiltrotor aircraft.