Experimental investigation on flow structures of steadily translating low-aspect-ratio wings in low Reynolds number flow

In recent decades, Micro Air Vehicles (MAVs) have been a hot topic for their promising future. But the promotions of MAVs are hindered by their short endurances. To solve this problem, inspirations are brought from migratory butterflies who utilize the ‘flapping-gliding’ skill during long-distance migration to improve the flight efficiency. The butterfly’s gliding flights, which can be simplified by considering the steadily translating fixed wings, have drawn high attentions. Previous studies mainly focus on the aerodynamics of the low-aspect-ratio fixed wings at Re ≈ 105 via force measurements. However, few experimental studies have measured the 3D flow fields. Consequently, the underlying high lift-to-drag ratio mechanisms in the steadily translating butterfly-shaped wings are still not clear. To shed new light on this problem, the 3D flow structures around butterfly-shaped wings were captured and investigated in detail.