An experimental study of the aerodynamics of micro corrugated wings at low Reynolds number

In this paper, an experimental study was performed to examine the flow characteristics of fabricated micro corrugated wings by fully mimicking the real 3D Odonata wing. For this purpose, a true scale hind wing from the Orthetrum caledonicum species with a semi span length of 60 mm was reconstructed by non-destructive close-range photogrammetry and fabricated with an advanced 3D printer. The accuracy of the proposed reconstruction technique was evaluated and compared with a 3D model of the same wing created using a Micro-Computed Tomography (CT) scanning technique to show that the close-range photogrammetry method was able to predict the pattern of micro corrugation of the wings with satisfactory fidelity. To do that, the corrugation patterns of both reconstructed wings were compared at different sections of the wings. Then, high-resolution Particle Image Velocimetry was used to investigate the flow field of the wing during gliding flight at three low Reynolds numbers Re = 5 x 10(3), Re = 8 x 10(3) and Re = 12 x 10(3), and angle of attack 10 degrees. The results include free stream velocity, vorticity distribution, boundary layer, and flow visualization. The velocity contour and vorticity boundary layer of both wings were compared experimentally. The flow behavior around the corrugated patterns reconstructed from both methods were compared with satisfactory agreement. The results support that the corrugations of the wing act as turbulators to generate unsteady vorticity to transition the boundary layer from laminar to turbulent quickly, leading to delayed stall and improved aerodynamic performance. Moreover, this study shows the application of the presented photogrammetry method for corrugated wing reconstruction, which is fast, low-cost, non-destructive, with high replication accuracy for the next generation of micro air vehicles.

Automated summary

This paper experimentally examines the flow characteristics of fabricated micro corrugated wings by mimicking real 3D Odonata wing using close-range photogrammetry and 3D printing. The study shows that the corrugations act as turbulators to improve aerodynamic performance by generating unsteady vorticity. The photogrammetry method used for wing reconstruction is fast, low-cost, non-destructive, and offers high replication accuracy for future micro air vehicles.