The numerical analysis of forward fan noise shielding effect on the Over-the-Wing Nacelle configuration

The noise shielding characteristics of the Over-the-Wing Nacelle (OWN) configuration are numerically investigated in the experimental setup. Linearized Euler equations are solved on the block-structured Cartesian mesh method named Building-Cube Method (BCM) to resolve the noise accurately. First, the noise propagation from the isolated nacelle is computed and the noise characteristics are compared with experiment to confirm the characteristics of noise source. Next, the noise shielding metrics in three nacelle positions are computed and the Overall Sound Pressure Levels (OASPLs) of noise shielding metrics are compared with experiment. Computed OASPL shows good agreement with experiment. OASPLs increase as the nacelle position moves backward. In the comparison of noise shielding characteristics of each frequency component, the configuration of forward nacelle position results in lower noise shielding metric in higher frequency. On the other hand, the configurations of backward nacelle position show higher noise shielding metric in higher frequency. Finally, the nondimensional pressure distributions on model surface are compared. It is verified noise from nacelle is shielded by the wing-fuselage configuration. Furthermore, noise distribution of fuselage surface moves backward and forward as nacelle moves.