INVESTIGATION OF A NOVEL VTOL AIRCRAFT CONCEPT FOR OPERATIONS IN URBAN AREAS

Experimental investigation on a novel VTOL aircraft named “Anuloid” has been carried out to assess its aerodynamics performances. The study focused on two main aspects: the analysis of the Coanda effect on the 1:20 scaled model without cross-flow and the aerodynamic characterization of the body, performed on the 1:5 scaled model in a large wind tunnel. The first task included the study of the Coanda effect, both in hovering and in ground effect conditions. Basic and modified geometries for the fan duct outlet were also investigated and the influence of the Reynolds number was evaluated. A simplified preliminary analysis on the effectiveness of the maneuverability surfaces was finally conducted. Results evidenced that the Coanda effect is present only for the modified geometries of the outlet section, whereas the basic geometry gives rise to early flow separation. The wind tunnel tests highlighted that the aircraft has poor lift and high drag in normal flight condition, i.e. when α<0°. In addition to this, the pitching moment is negative in the whole range of incidences tested, resulting in longitudinal instability. Finally, pressure distributions revealed massive flow separation on both lower and upper surfaces that gives rise to a very complex unsteady and tridimensional flow field configuration around the body.