01. Experimental/Computational Fluid Dynamics

When birds land, an increase in the wing's angle of attack leads to flow separation, resulting in a loss of lift and an increase in drag. However, by allowing feathers to pop up under specific flight conditions automatically, the formation of flow separation is disrupted. This helps maintain attached airflow over the wing surface, thus generating lift more effectively. When flow separation occurs, a recirculation zone is formed, which allows bird feathers to lift automatically, preventing the separation zone's continuous spreading towards the wing's leading edge. This study mimics the behavior of bird feathers using self-actuated flaps to control flow separation. The lift can be maintained even after wing stall, achieving lift enhancement and improving the lift-to-drag ratio. This device offers the advantages of simple installation and significant performance improvement, making it suitable for application on unmanned aerial vehicles (UAVs). Particularly, it proves beneficial for military UAVs that often face the need for drastic pitch or large-angle-of-attack variations during mission execution.