A dragonfly shows a good performance in its flight at very low Reynolds number. The wing section of a dragonfly is thin and corrugated profile. The purpose of the present study is to ascertain the aerodynamic characteristics of the corrugated thin airfoil at very low Reynolds numbers range provided between 1000 and 10000. The thin aluminum wing models were made in imitation of the wing section of a dragonfly for this study. The specific low pressure wind tunnel developed by authors was used for measuring the very small forces and moments acting on the wing model. The lift, drag and pitching moment coefficients of the thin corrugated airfoils were discussed by comparing with those of thin flat plate in the same Reynolds number. When the corrugation was inserted in a profile of thin airfoil at an appropriate position, the minimum drag coefficient decreased and the maximum lift-to-drag ratio increased. From these results, it has been revealed that the corrugated thin airfoil such as dragonfly wings shows a good performance in the lift coefficient and the lift-to-drag ratio at Reynolds number less than 5,000. Further, it was worthy note that the minimum drag coefficient is small in comparison with that of the thin flat plate. It was found through the flow visualization in the water tank test that the fixed vortices seen in the concaves of the airfoil are effective at very low Reynolds number.
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