Study on the induced velocity and noise characteristics of a scissors rotor

Aerodynamic and acoustic experiments were carried out to investigate the induced inflow distribution and noise characteristics of a scissors rotor in hover. The aerodynamic experiment was conducted on a model rotor rig and the induced inflows for two different scissors rotor configurations (the L configuration and U configuration) were measured. The experimental results indicate that the induced velocity near the lower blades is consistently larger than that near the upper blades. A free-wake analysis was used to predict the aerodynamic characteristics. The variation of the induced velocity with different scissors angles was simulated analytically and the results were compared with test data. The acoustic experiment was conducted in an anechoic aeroacoustic laboratory and the noise levels for both the scissors rotor configuration and a conventional configuration were measured. The effects of different scissors angles on rotor noise were investigated. It was shown that the noise level of a scissors rotor depends on both the azimuthal and vertical spacing and is not necessarily less than that of a conventional configuration.