Leading-edge Serrations which Reduce the Noise of Low-speed Rotors |
Common terms and phrases
0015 airfoil section 1000 Basic rotor 18 Basic rotor 18 Serration 70 Sound pressure 9 10 Harmonics 90 Thrust acoustic acoustic data Aerodynamic background noise Basic rotor 12 Basic rotor Serration blade angles blade passage frequency Concluded Continued dB overall sound deg 12 Basic due to serrations effects of serrated electric motor Figure 18 Figure 20 figure of merit ft/sec Harmonics of blade high frequency noise indicate that serration leading-edge serrations level in dB levels at 7.6 levels at harmonics m/sec measured at microphone N/m² N/m2 120 Microphone Noise Measurement octave band overall noise levels overall sound pressure reduced the noise rotor 12 Basic rotor 12 Serration rotor A 18 rotor axis rotor blade rotor center rpm f₁ Serration 3 18 Serration 3 Serration serration shape shown in figure Small-Scale Rotor Test Sound pressure level stagnation point test stand Thrust and torque tip Reynolds numbers tip speed ОО