Lift enhancement via leading edge vortex delay in flapping flight utilizing kinematic modifications

Flapping-winged micro aerial vehicles (MAVs) are an innovative approach to indoor flight, useful for reconnaissance. However, challenges remain in improving the maneuverability of these drones in low-speed flight, specifically using wing kinematics for different flight profiles. This work focuses on the plunge motion of the SD7003 airfoil in forward flight. Unsteady simulations are carried out at a Reynolds number of 10,000 in Ansys Fluent upon validation against experimental, theoretical, and numerical results from literature. Modification of the kinematics is performed by skewing the sinusoidal curve that dictates the effective angle of attack of the airfoil, leading to what is termed “peak-shifted” (PS) kinematics. The skewness of the curve is varied systematically to delay the peak of plunge velocity during the downstroke. Due to this, the leading edge vortex formation and shedding were also found to be delayed, with stronger vortex cores causing a surge in lift force. Results indicate that with the PS kinematics, mean lift increased by 4.5% and mean drag reduced by 7.9%, at the cost of an increase in power requirement of 42.9% compared to the baseline kinematics. Since lift augmentation and drag reduction are obtained with no change in plunge amplitude or frequency, this opens up opportunities in tail-less MAV design to use PS kinematics in short intervals for maneuvers or flight controls, including roll, pitch, and yaw.