Open-rotor engine noise analysis based on Mohring acoustic analogy

In order to systematically study the characteristic of open-rotor noise in non-uniform flow field, CFD (computational fluid dynamics)/CAA (computing aerodynamic acoustic-s) hybrid method of the open-rotor aerodynamic noise was set up. The aerodynamic characteristics of open-rotor were analyzed through compressible modified Spalart-Allmaras turbulence model method, then, the open-rotor noise and noise transmission were numerically simulated by acoustic infinite element method. At the same time, the average flow field and its smooth interpolation were introduced to acoustic grid as a background flow field. Taking into account the noise distribution chart and the far field feature point spectrum curve, it was concluded that non-uniform flow field radiated noise in the open-rotor engine was mainly focused on low frequency range, the maximum noise was 142dB, and the maximum noise frequency was 115Hz. With the increase of frequency, multiple local peak sound pressures appeared alternately, and noise attenuation rate decreased. A method was proposed to predict the noise for the next generation open-rotor engine.