Simulation of Unsteady Aerodynamics of the Unmanned CRWDragonfly Aircraft Hovering Near the Ground

摘要

A computational study of the flow field characteristics, rotor performance and airframe aerodynamic forces and moments of the unmanned X-50 Dragonfly aircraft was performed for a hovering flight in and out of ground effect. Unsteady simulations were performed for different ground heights using a three-dimensional Navier-Stokes solver (Rot3DC). For each case, airframe pressure distributions, forces and moments, and velocity profiles were calculated. This investigation showed that hover height above ground had a significant effect on both the steady and unsteady vehicle forces and moments. As the aircraft height above the ground increased, force and moment unsteadiness grew in amplitude until the X-50 surpassed a critical height, at which point the unsteadiness in forces and moments begin to dissipate. When the aircraft was far enough above the ground (OGE) the forces and moments on the aircraft remained essentially constant. The effects of the unsteady ground effects on the rotor performance was also investigated, as was the effect of horizontal tail incidence on the unsteady airframe pitching moment.