Effects of Tip Dihedral on Aerodynamics of Hovering Tilt Rotor

The tilt rotor has attracted great interest due to the combined advantages of both helicopters and propeller aircraft, but it also faces more complex aerodynamic challenges. At hovering condition, the shedding tip vortex impinges on the adjacent blade and induces an open separation on the suction surface, while little research has analyzed the detailed influence. This paper aims at investigating the aerodynamics of hovering tilt rotor with the tip dihedral design. The mechanisms of the tip dihedral effects on the vortex-induced separation and blade–vortex interaction are examined using the numerical and experimental methods. The results show that the vortex-induced separation is dominated by the radial pressure gradient, which is achieved through affecting the migration of low-momentum fluid on the suction surface. Besides, the tip dihedral design alters the blade–vortex interaction by changing the tip vortex strength and blade–vortex distance and hence leads to the redistribution of incidence. The combinations of these two mechanisms contribute to the tip dihedral effects on the overall performance of hovering tilt rotor, and their applied ranges are also analyzed based on the experimental observations. These findings provide valuable insights into the tip dihedral effects and support the development of next-generation low-altitude aircraft.