Pressure Variations for a Shrouded Tail Rotor in Edgewise Flight

The concept of a shrouded rotor has gained considerable attention in modern rotorcraft design due to its potential to improve the aerodynamic and aeroacoustics performance of the rotor. By enclosing the rotor within a cylindrical shroud, additional thrust can be generated while achieving considerable noise reduction. Most existing research has focused on the hovering condition, assuming a zero-freestream velocity. However, during the climb and descent, the shrouded tail rotor operates in an edgewise flight condition, leading to observable inflow distortion. In this study, a shrouded rotor was experimentally examined in a wind tunnel at various tip-to-freestream velocity ratios μ. Measurements of the pressure distribution on the shroud inner surface were investigated, which showed a clear change in topology as μ increased. A peak positive pressure was observed on the downwind side of the shroud, which moved towards the shroud exit as μ increased.