Abstract
Globalization has led to an increase in the use of small copters for different activities such as geo-referencing, agricultural fields monitoring, survillance, among others. This is the main reason why there is a strong interest in the performance of small-scale propellers used in unmanned aerial vehicles. The flow developed by rotors is complex and the estimation of its aerodynamic performance is not a trivial process. In addition, viscous effects, when the rotor operates at low Reynolds, affect its performance. In the present paper, two different computational methods, Computational Fluid Dynamics (CFD) and the Unsteady Vortex Lattice Method (UVLM) with a viscous correction, were used to study the performance of an isolated rotor of a quadcopter flying at hover. The Multi Reference Frame model and transition S S T κ − ω turbulence model were used in the CFD simulations. The tip vortex core growth was used to account for the viscous effects in the UVLM. The wake structure, pressure coefficient, thrust and torque predictions from both methods are compared. Thrust and torque results from simulations were validated by means of experimental results of a characterization of a single rotor. Finally, figure of merit of the rotor is evaluated showing that UVLM overestimates the efficiency of the rotor; meanwhile, CFD predictions are close to experimental values.
Highlights
Unmanned Aerial Vehicles (UAVs) is a growing technology developed to be used in different applications such as geo-referencing, agricultural monitoring and security among many others.Within platforms available to build UAVs, the quadcopter is one of the most used, as it is a VerticalTakeoff and Landing (VTOL) Vehicle, easy to maneuver and to control
The aerodynamic behavior of these vehicles depends on the efficiency of the rotors and, its performance is strongly affected by the wake developed by a single rotor and its interaction with the other rotors and fuselage
It is important to mention that the visualized Q criterion field corresponds to one estimated from the vorticity field observed from the non-inertial reference frame
Summary
Unmanned Aerial Vehicles (UAVs) is a growing technology developed to be used in different applications such as geo-referencing, agricultural monitoring and security among many others.Within platforms available to build UAVs, the quadcopter is one of the most used, as it is a VerticalTakeoff and Landing (VTOL) Vehicle, easy to maneuver and to control. Momentum theory and the blade element theory are theoretical approximations to estimate thrust (CT ) and power (CP ) coefficients, but these are based on strong fluid simplifications. Further refinements of these models were constructed based on empirical parameters obtained by experimental studies of rotors used in helicopters; the applicability of these data to study small rotors is not advisable. These techniques can be employed as good preliminary approximations [1]
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