Numerical Investigation on Interactional Aerodynamics of Quadcopter in Hovering and Vortex Ring States

Abstract

This study numerically investigates interactional aerodynamics of a quadcopter in hover and descent conditions including the vortex ring state. The primary objective is to understand major flow structures and their impact on unsteady airloads of multirotor aircraft. Unsteady simulations are conducted here, using an overset mesh approach with the OpenFOAM flow solver. Interactional aerodynamics from multiple rotors and a fuselage alters the rotor inflow, compared to a single rotor, in hover. The current study indicates that a quadcopter encounters major thrust fluctuation in 2/rev with additional thrust fluctuation in 4/rev and 8/rev because of locally varied inflow due to rotor-rotor and rotor-fuselage interactions. In the second part of the thesis, rotor phases are varied in order to examine a potential approach of phase control to mitigate vibratory airloads. This study identifies the optimal rotor phase for the minimal aerodynamic fluctuation of the current quadcopter. A novel superposition approach of the individual rotor airload is proposed for a multicopter configuration here, and this superposition approach helps to reduce massive computations of a whole multicopter with various rotor phases. In the third part of the thesis, the quadcopter in descent conditions, including the vortex ring state, is simulated to investigate interactional aerodynamics in the vertical flight. In summary, this study numerically investigates the interactional aerodynamics of the quadcopter, focusing on three main topics: (1) rotor-rotor and rotor-fuselage interactions in hover, (2) rotor phase control for mitigating vibratory airloads, and (3) interactional aerodynamics on the flow field and unsteady airloads in descent conditions including the vortex ring state. This study provides insights into the interactional aerodynamics of multirotor aircraft, which could contribute to identifying sources of unsteady airloads and reducing aerodynamic fluctuation using rotor phase control. Furthermore, this study offers insights into flow structure and fluctuating airloads of multirotor aircraft in descent and the vortex ring state.