Aerodynamic interference analysis of multiple rotors in a heterogeneous unmanned aircraft system

Abstract

In recent years, with the development of intelligent technology, rotorcrafts have been widely used in unmanned collaborative missions due to their excellent maneuverability and vertical flight capability. However, the flight process of rotorcrafts generates a noticeable induced flow that affects the flight safety of surrounding aircrafts. In the current research on the aerodynamic interference of multiple rotorcrafts, scholars are focusing on the effects of the upper rotor on lower rotors, while ignoring the induced influence of lower rotors. In this research, the detached eddy simulation was used to analyze the numerical and flow characteristics of an upper small-ducted-rotor (SDR) disturbed by a large-rotor (LR). The Q-criterion and power spectrum density method were employed to analyze the wake vortex evolution characteristics of the SDR. The results indicate that the thrust loss of the duct is significantly positively correlated with the rotational speeds of both SDR and LR, whereas the thrust loss of the rotor is only associated with the rotational speed of LR. The thrust loss of the duct is significantly greater than that of the rotor, primarily due to the disruption of attachment vortices and the generation of new shear-layer shedding vortices. Wake analysis reveals that the disturbance from LR simultaneously enhances both the kinetic and turbulent kinetic energy around SD, resulting in the discovery of multiple energy peak frequencies in the near- and mid-field distinct from the blade-passing frequency. This research helps analyze rotorcrafts' flight safety during the collaborative processes.