기체 형상이 로터-기체 상호작용 소음에 미치는 영향에 관한 전산해석

Abstract

Urban Air Mobility(UAM) or Advanced Air Mobility(AAM) has emerged as a next-generation transportation system based on electric-powered vertical takeoff and landing aircraft. Distributed Electric Propulsion(DEP) system is applied to most UAM aircraft, which inevitably accompanies an increase in the number of rotors or propellers, thus leading to a strong interaction between the rotor and the airframe. This study conducted a computational investigation of the effects of rotor-airframe interaction on aerodynamic performance and noise generation depending on the airframe shapes. Aerodynamic analysis was performed using Lattice Boltzmann Method(LBM) simulation, and the noise level was predicted using the Ffowcs Williams-Hawkings(FW-H) acoustic analogy with permeable boundary condition. Two different types of airframe geometry were considered: cylinder and conical airframes. The thrust coefficient of rotor blades with the conical airframe is higher than that of rotor blades with the cylinder airframe. Tip vortex breakdown phenomenon and transition into turbulent wake state were captured in both airframes. Moreover, it was observed that high-intensity noise was radiated over the broad surface of the airframe for the conical airframe case. The comparison of overall sound pressure level(OASPL) on the hemisphere showed the strong interaction between the rotors and conical airframe causes a considerable increase in the noise level, compared to the isolated rotor and rotor-cylinder airframe.