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首页> 外文期刊>Journal of Fluids and Structures >Wing performance and 3-D vortical structure formation in flapping flight
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Wing performance and 3-D vortical structure formation in flapping flight

机译：扑翼中的机翼性能和3-D旋涡结构形成

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Numerical simulations of the three-dimensional flow around a modelled insect wing were performed to investigate the performance in flapping flight and to provide insight into the vortex dynamics and associated force generation. Different parameters relevant for three-dimensional flapping wing aerodynamics have been studied, notably the angle of attack in mid-stroke, the Rossby number, the Reynolds number and the stroke kinematic pattern. A parametric study has been made for these parameters, notably for the hovering flight regime. The leading-edge vortex is confirmed to be important for the gain in lift, it being larger and more stable at angles of attack larger than about 30°. At smaller angles of attack, the leading-edge vortex development is insufficient to increase the lift, instead the lift decreases. It is observed that the trend of the force development over the cycle and the effect of the angle of attack is similar for revolving and translating wings. However, a flapping wing motion with a revolving character has an important lift-enhancing effect, at a small penalty of drag. Although the variations in lift and drag with Reynolds number are found to be larger at lower Rossby numbers, the lift-enhancing effect of the revolving wing appears not strongly dependent on Reynolds number. Application of a 'trapezoidal angle of attack' pattern with increased angular rotation at stroke reversal showed a significant performance increase. It was further shown how the variation in lift and drag can be significantly influenced by introducing deviation in the stroke pattern. A comparison between the three-dimensional simulations and two-dimensional simulations (for forward flight conditions) displayed similar trends with respect to the influence of the angle of attack. However, the latter do not account for finite wing and tip vortex effects which were found to have an important impact on the LEV development.
机译：围绕建模的昆虫机翼进行三维流动的数值模拟，以研究扑翼飞行的性能，并提供对涡旋动力学和相关力产生的见解。研究了与三维襟翼空气动力学有关的不同参数，特别是中风的迎角，Rossby数，雷诺数和行程运动学模式。已经针对这些参数进行了参数研究，尤其是针对悬停飞行状态。前沿涡流被证实对于提升升力很重要，它在迎角大于约30°时更大且更稳定。在较小的迎角下，前沿涡旋发展不足以增加升力，反而升力降低。可以看出，在旋转和平移机翼时，力在整个循环中的发展趋势和迎角的影响是相似的。但是，具有旋转特性的襟翼运动具有重要的升力增强效果，但阻力很小。尽管在较低的罗斯比数下升力和阻力随雷诺数的变化较大，但旋转机翼的升力增强效果似乎并不强烈依赖于雷诺数。在冲程反转时增加角度旋转的“梯形攻角”模式的应用显示出显着的性能提升。进一步显示了如何通过在行程模式中引入偏差来显着影响升力和阻力的变化。三维模拟和二维模拟（针对向前飞行条件）之间的比较显示了在迎角影响方面的相似趋势。但是，后者并不能说明有限的机翼和叶尖涡流效应，而有限的机翼和叶尖涡流效应对LEV的发展具有重要影响。

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