Enhancement of aerodynamic performance of a bristled wing by elliptic cylinders.

Enhancing the aerodynamic performance of bristled wings is an important topic for small flying robotics. This paper numerically investigates this situation at very low Reynolds numbers by using elliptic cylinders as the bristles instead of circular cylinders. Optimal configuration of the bristled wing with five elliptic cylinders is obtained, which corresponds to the maximum lift. The results show that, compared with the case of circular cylindrical bristles, the aerodynamic performance of the elliptical bristles can be enhanced effectively. The enhancement can be more significant as the aspect ratio of the ellipses increases and the gap width decreases. The bristled wing generates more lift compared to a flat-plate wing with a length five times that of the major axis of an ellipse. For the cases that the attack angle α for the whole wing is equal to those for the elliptical bristles θ , the optimal attack angle for ellipses maximizing the total lift force of the five-bristle model is between 40° and 45°. For α ≠ θ with the Reynold number Re ≪ 0.1, the optimal ellipse attack angle is between 40° and 45°. For α ≠ θ with Re ∼ 1, the optimal ellipse attack angle deviates heavier from the range between 40° and 45° at some α values and reaches approximately 32° at α = 20°. This paper can lay a foundation for optimal design of small flying robotics and enhancement of flow through porous structures in future.