A flexible flapping wing with a rectangular planform was designed to investigate the influence of flexible deformation. This planform is more convenient and easier to define and analyzed its deforming properties in the direction of spanwise and chordwise. The flapping wings were created from carbon fiber skeleton and polyester membrane with similar size to medium birds. Their flexibility of deformations was tested using a pair of high-speed cameras, and the 3D deformations were reconstructed using the digital image correlation technology. To obtain the relationship between the flexible deformation and aerodynamic forces, a force/torque sensor with 6 components was used to test the corresponding aerodynamic forces. Experimental results indicated that the flexible deformations demonstrate apparent cyclic features, in accordance with the flapping cyclic movements. The deformations in spanwise and chordwise are coupled together; a change of chordwise rib stiffness can cause more change in spanwise deformation. A certain lag in phase was observed between the deformation and the flapping movements. This was because the deformation was caused by both the aerodynamic force and the inertial force. The stiffness had a significant effect on the deformation, which in turn, affected the aerodynamic and power characteristics. In the scope of this study, the wing with medium stiffness consumed the least power. The purpose of this research is to explore some fundamental characteristics, as well as the experimental setup is described in detail, which is helpful to understand the basic aerodynamic characteristics of flapping wings. The results of this study can provide an inspiration to further understand and design flapping-wing micro air vehicles with better performance.

中文翻译：

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矩形平面扑翼的柔性变形实验研究

设计了具有矩形平面形状的柔性襟翼，以研究柔性变形的影响。该平面图更方便，更容易定义和分析其沿翼展方向和弦向的变形特性。拍打的翅膀是由碳纤维骨架和聚酯薄膜制成的，尺寸与中型鸟类相似。使用一对高速相机测试了其变形的灵活性，并使用数字图像相关技术重建了3D变形。为了获得挠性变形与空气动力之间的关系，使用具有6个组件的力/扭矩传感器测试相应的空气动力。实验结果表明，柔性变形表现出明显的周期性特征，按照拍打的周期性运动。翼展方向和弦向的变形耦合在一起。弦向肋骨刚度的变化会引起翼展方向变形的更多变化。在变形和拍打运动之间观察到一定的相位滞后。这是因为变形是由空气动力和惯性力两者引起的。刚度对变形有重大影响，进而影响空气动力学和动力特性。在本研究的范围内，刚度中等的机翼消耗的功率最小。这项研究的目的是探索一些基本特性，并详细描述实验装置，这有助于理解襟翼的基本空气动力学特性。