Numerical Simulation and Flow Display of Bionic Alula on Rectangle Airfoils

Some birds have small wings (Alula) in the middle of their main wings. These small wings will tilt upward when the bird flies at a high attack angle to maintain a stable flying posture. This paper explores the lift effects of bionic Alula on rectangular airfoils with different aspect ratios through numerical simulation and flow display experiments. According to the numerical simulation, Alula can increase the rectangular airfoil lift coefficient by a maximum of 24% when the airfoil aspect ratio is 2. By comparing simulation results with flow display results, the low-pressure area generated by Alula and the merge of the Alula vortices with the airfoil tip vortices mainly contribute to the lift enhancement.