Abstract
Aerodynamic interactions between rotors are important factors affecting the performance of in-plane multirotor Unmanned Air Vehicles (UAVs) or drones, which are the majority of small size UAVs (or mini-drones). Optimal design requires knowledge of the flow features. The low Reynolds number of many UAV rotors raises the question of how these features differ from those expected by traditional analytical methods for rotorcraft. Aerodynamics of a set of side-by-side rotors in hover over a range of rotor separation and Reynolds number is studied using high-speed Stereo Particle Image Velocimetry (SPIV) and performance measurements. The instantaneous and time-averaged SPIV data presented here indicate an increase in inter-rotor wake interactions with decrease in rotor spacing and Reynolds number. A dip in rotor efficiency at small rotor spacing at low Reynolds number is observed through thrust and torque measurements. The basic components of in-plane multirotor wake and velocity profiles are identified and discussed to help generalize the findings to a wide range of drones. However, the data provide confidence in traditional analysis tools, with small modifications.
Highlights
Quadcopters, hexacopters, and in-plane octocopters appear to dominate the current commercial and recreational markets for Vertical Takeoff Landing Unmanned Air Vehicles (UAVs) (VTOL UAVs)
The loadcell readings in Newtons and Newton-meter for thrust and torque, respectively, are converted to the non-dimensional Coefficient of Thrust (CT ) and Coefficient of Torque (CQ ) form to account for the variations in rotor speed and dimensions while comparing among cases
The coefficients of thrust and torque are used to find Figure of Merit (FM) which is a measure of efficiency of a rotor compared to the theoretical best found using the momentum theory
Summary
Quadcopters, hexacopters, and in-plane octocopters appear to dominate the current commercial and recreational markets for Vertical Takeoff Landing UAVs (VTOL UAVs). These configurations offer much higher flexibility in size and placement of rotors and payload when compared with traditional single rotor or coaxial rotor configurations. A recent paper by Gonzalez et al [1] gives an overview of types of UAVs, describes all the necessary subsystems with their importance, and mentions a few present day applications. Floreano et al describe the potential of small size UAVs to a great extent and cover all important current challenges on different fronts which need to be addressed, in their review paper [2]. The authors rightly make an observation that aerial vehicles do not scale down well in terms of aerodynamic efficiency, affecting performance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
