Angling for aerodynamic improvements in drones

The increasing use of unmanned aerial vehicles (UAVs) has stimulated a great deal of aerodynamic research. Much has focused on the angle of attack (AOA) – the angle between airfoil and airflow – as it plays a major role in flight maneuverability, efficiency, and stability. UAVs are often designed to operate with AOAs that far exceed those of larger aircraft, with some exceeding 45°.

Many investigations of high-AOA flow dynamics have employed computational methods, but these have limited flow pattern predictive accuracy, leaving a lot to be learned about flight performance in turbulence.

Somashekar and Vinod used a two-equation eddy-viscosity model to investigate AOAs up to 90° under low-speed conditions, offering fresh insight on airfoil behavior and aerodynamic performance during turbulence and flow separation.

“Our study provides a deeper understanding of how small drones can maintain control and efficiency even at steep angles, which is crucial for applications like urban surveillance, search-and-rescue missions, and military reconnaissance,” said author V. Somashekar.

The researchers observed that the airfoil generates increasing lift up to an AOA of 11°, but that even at angles up to 90°, it can still retain some lift. They also found that drag rises significantly at mid-range AOAs due to flow separation. However, despite increasing drag, the lift-to-drag ratio actually improves at very high AOAs, suggesting that even at extreme angles, the airfoil retains efficiency, which bolsters UAV maneuverability.

“These small aircraft often fly at steep angles, so understanding their aerodynamic performance helps in designing better platforms,” said Somashekar. “Our findings offer valuable data for drone design to allow for handling aggressive maneuvers without excessive drag or loss of control.”

Source: “Predicting the high-angle-of-attack characteristics of an airfoil for micro/unmanned aerial vehicle applications,” by V. Somashekar and L. Vinod, International Journal of Fluid Engineering (2025). The article can be accessed at https://doi.org/10.1063/5.0233018 .