Abstract:
In order to study the influence of blade elastic deformation on rotor aerodynamic noise, based on Camrad Ⅱ and the FW-H equation, an aerodynamic noise calculation model that takes the blade elastic deformation into account has been established for a rotor in hover. The elastic blade model in Camrad Ⅱ is used to calculate the elastic shape variation of the blade. A three-dimensional grid is used to accurately describe the deformed blade. Combined with the unsteady aerodynamic load of the rotor obtained by Camrad Ⅱ, the hovering noise of the deformed blade is calculated and analyzed based on the FW-H equation. The binocular stereo vision method is used to measure the deformation of the model rotor in a wind tunnel. It is found that the numerical results are agree reasonably well with the experimental data, which verifies that Camrad Ⅱ has a good reliability and can accurately predict the elastic shape variation of the blade in hover. The hover noise characteristics of the full scale rotor are further calculated and analyzed. The results show that under typical working conditions, the rotor blade has obvious elastic deformation, especially in the flap direction. The blade deformation does not change the directivity of the noise in hover. However, it affects the thickness and loading noise in the main propagation direction, resulting in a maximum variation of about 1.0 dB in the total noise. Consequently, the influence of the blade elastic deformation should be considered for obtaining more accurate aerodynamic noise.