Abstract
To study the aerodynamic performance of hovering octorotor small unmanned aerial vehicles (SUAV) with different rotor spacing, the computational fluid dynamics (CFD) method is applied to analyze the flow field of an octorotor SUAV in detail. In addition, an experimental platform is built to measure the thrust and power of the rotors with rotor spacing ratios L/D of 1.0, 1.2, 1.4, 1.6, and 1.8, sequentially. According to the theory of momentum, rotor aerodynamic performance is obtained with qualitative analysis. Further analysis with numerical simulation is presented with the flow field of the octorotor SUAV, the vorticity distribution, velocity distribution, pressure distribution, and streamline. The results show that the aerodynamic performance varies with the rotor spacing. Specifically, the aerodynamic performance is poor at L/D = 1.0, which is accompanied with strong interaction of wake and tip vortexes and interaction with each other. However, the aerodynamic efficiency is much improved with a larger rotor spacing, especially achieving the highest at L/D = 1.8, which is considered to be the best rotor spacing ratio for this kind of octorotor SUAV.
Highlights
Small unmanned aerial vehicles (SUAVs) are normally less than 25 kg and easy to pack
The main research objective of this paper is to explore how the aerodynamic performance of a small octorotor small unmanned aerial vehicles (SUAV) changes with a change of rotor spacing, why it changes, and whether there is an optimal rotor spacing
The aerodynamic performance of the rotors change with a change of rotor spacing, but this change
Summary
Small unmanned aerial vehicles (SUAVs) are normally less than 25 kg and easy to pack. The octorotor SUAVs with evenly distributed rotors have been widely used in agricultural, surveillance, and military, due to its advantages of simple operation and convenient portability. Octorotor SUAVs have higher load and more damaged redundancy as compared with a quadrotor or hex-rotor SUAVs. Considering that octorotor SUAVs often operate in environments where the Reynolds numbers are less than 105 , viscosity, laminar separation bubbles, thickened boundary layer, and flow separation influence the rotor tip, which can lead to increased drag on the vehicle, resulting in poor aerodynamic performance. With the help of constantly developing computer simulation technology, we can intuitively explore the reasons that lead to a decrease or increase in aerodynamic performance of the rotor, and help to optimize the layout of the SUAVs
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