摘要: Laboratory measurements of the acoustic and aerodynamic performance of a highly twisted eighteen-inch diameter two-bladed rotor are evaluated to understand the mechanisms responsible for generating rotor broadband noise from rotor... 展开 Laboratory measurements of the acoustic and aerodynamic performance of a highly twisted eighteen-inch diameter two-bladed rotor are evaluated to understand the mechanisms responsible for generating rotor broadband noise from rotors of this scale. Rotor speeds are varied between 30 and 132 revolutions per second, which equates to blade tip Mach numbers between 0.13 and 0.56, and chord-based Reynolds numbers between 6.6×10~4 and 2.6×10~5, respectively. Microphones are biased towards locations above the rotor disk plane where Doppler effects and noise from the turbulent wake are less likely to corrupt sound measurements, and where the boundary layer structures on the suction side of the blade are likely to be more mature. Harmonics and subharmonics of the blade pass frequency noise are removed to reveal features attributed to both turbulent boundary layer trailing edge noise and, in some instances, separated flow noise. When the blade tip Mach number is greater than 0.3, peak pressures associated with the turbulent boundary layer noise are shown to scale with M~(4.4), and to scale with peak frequencies by F~(6.7). A moving source model is then proposed for localizing positions on the rotor blade where turbulent boundary trailing edge noise is most prominent. The model is empirical and leverages measurements of the boundary layer properties of static airfoils to estimate characteristic scales that are believed to contribute to rotor broadband noise. The moving source model persistently identifies noise sources near the tip of the rotor that migrate towards the rotor hub with increasing rotor speed. 收起