로터-기체 상호작용 소음에 관한 수치 예측 연구

Abstract

Strong-intensity tip vortex generated from the tip of the rotor blade causes strong aerodynamic interactions with the fuselage and structures. This interaction phenomenon directly affects the aerodynamic performance and noise characteristics of the rotor blades. In this study, the computational analysis of rotor-airframe configuration is performed to investigate the effects of rotor-airframe interaction on thrust, wake structure, flow field, and noise levels using the Lattice-Boltzmann Method (LBM). The isolated rotor operating in hovering conditions is used for the validation model. The thrust force and tonal noise associated with the 1st and 2nd Blade Passage Frequency (BPF) of the isolated rotor are compared against the measurements. The validation results showed good agreement with the experimental data. When a conical airframe is placed under the rotor blade, the thrust force tends to oscillate periodically. In addition, rotor wake development along the downstream direction is obstructed, and asymmetric wake structure can be observed, thus leading to a faster tip vortex breakdown and an increase in turbulence intensity. Finally, the overall sound pressure level (OASPL) of the rotor-airframe is higher than that of the isolated rotor at all microphone positions due to thrust fluctuation and a highly unsteady flow field caused by the strong interaction.