Computational Study of Wake Interaction and Aeroacoustic Characteristics in Multirotor Configurations

摘要

Multirotor configurations such as VTOL and urban air mobility have been focused on today due to the high maneuverability. Aerodynamic and aeroacoustic characteristics of multirotor have much difference to those of a single rotor. In this study, a numerical analysis based on the free wake vortex lattice method is used for identifying the wake interaction effect. In order to compare the various configurations and operating conditions, the effects of the spacing between the rotors in hovering flight and the effects of the advancing ratio and the formation in forward flight are discussed. Aerodynamic and aeroacoustic characteristics are significantly affected by the wake interaction. In the hovering flight, the unsteady loading of multirotor changes periodically and loading fluctuation increases as decreasing the spacing. It causes the variation in unsteady loading noise and the noise directivity pattern. In the forward flight, the difference in loading fluctuation and noise characteristics are observed according to the diamond and square formation of rotors. By comparing with results which obtained by using single rotor analysis for multirotor configurations, multirotor has different directivity pattern according to the location of each rotor. As a result, wake interaction effect becomes a highly important factor for aeroacoustic analysis according to multirotor configurations and operating conditions.