Park Y., Kim S., Bin J., Lee S.

In general, discrete frequency acoustic modes are generated in the aircraft fan engine by rotor-stator interaction. Moreover, it is reported that the scarfed aero-intake of the engine has an effect on the directivity pattern of the radiated sound field. In this study, the propagation of discrete frequency acoustic modes is numerically simulated, and the propagation characteristics and the directivity patterns of the scarfed engine are investigated. The near-field solution is calculated with the high order DRP(dispersion-relation-preserving) scheme based on the time-domain computational aeroacoustics for the three-dimensional linearized Euler equations. In addition, the Kirchhoff integral method is applied for the calculation of the far-field directivity pattern. For the computational efficiency, a parallel computing technique is applied in the near-field simulation. Furthermore, an overset and a patched grid technique are implemented to the complex aero-intake geometry. In order to validate the numerical method, the axi-symmetric aero-intake solution with zero thickness is compared with the analytic solution. Through the comparison between the directivity patterns of the scarfed and normal aero-intake, it is found that the scarfed aero-intake reduces the noise propagation to the ground by reflecting more noise upward.