Experiment on thickness noise of rotor based on control of active trailing edge

An on-blade control technique to reduce thickness noise was developed based on the principle of sound field cancellation. A high-accuracy method for calculation of helicopter rotor aerodynamic noise was established based on the Ffowcs Williams-Hawkings (FW-H) equations with the control of active trailing edge. The overall experimental scheme was designed and the open-loop experiment of active noise control was carried out in a fully anechoic chamber, and the experiment data were compared with theoretical calculation to verify the validity of the method and experiments results. The parameter influences of the amplitude, frequency and initial phase of the trailing edge deflection on the thickness noise reduction of the rotor were analyzed. The influences of the observation distance on the cancellation of rotor thickness noise were then deeply assessed. The experimental results demonstrated that there was an optimal phase at each frequency to minimize the noise at the observations, and it varied with different frequencies; the reasonable trailing edge control law can effectively reduce the thickness noise of the observation points in the plane of the rotor up to 2-3 dB.