论文部分内容阅读
扑翼飞行器是未来航空领域的重要发展方向之一,而鸟类、昆虫等自然界的飞行生物所具有的出色飞行能力,为人造扑翼飞行器的设计工作提供了很好的参照。本文以鸟类的扑翼飞行为研究背景,针对简化的二维S1223翼型的刚性俯仰-沉浮运动,对其非定常气动力特性进行了数值研究。研究采用了动态混合网格技术以及非定常数值计算方法。为了提高动态混合网格的变形能力,采用了基于径向基函数的插值方法求解空间点的位移,翼型整个俯仰-沉浮运动周期内计算网格均维持了较好的质量,没有发生网格重构。非定常算法方面,通过约束单元边界面的法向速度从而满足了运动网格下几何守恒律的要求。空间离散采用了二阶的有限体积格式,时间离散则采用了双时间步和BLU-SGS相结合的隐式时间推进策略。计算得到了不同下拍时间、不同拍动角等条件下的升力、推力以及能耗,对其升力、推力产生机制进行了分析,并通过对气动力以及流场进行对比,分析了各拍动参数的影响。计算结果表明,翼型自身的“静态因素”是其产生升力的主要原因,非定常流动对增加升力起到了促进作用,而下拍时间、拍动角等运动参数对翼型的气动性能影响较大。当下拍时间占到整个拍动周期的约65%-70%时,单位能耗下的时均升力最大,该结论和观测数据较为一致。此外,通过对比分析得到了一组具有较好气动特性的拍动角参数,为后续针对三维问题的研究提供了参考。
Flapping-wing aircraft is one of the important development directions in the aviation field in the future. The excellent flying ability of flying creatures such as birds and insects provides a good reference for the design of artificial flapping-wing aircraft. In this paper, based on the study of bird’s flapping-wing flight, the unsteady aerodynamic characteristics of a simplified two-dimensional S1223 airfoil are studied numerically. The study uses a hybrid dynamic mesh technique and unsteady numerical methods. In order to improve the deformation ability of dynamic hybrid meshes, a radial basis function interpolation method was used to solve the displacement of space points. The calculated grids maintained good quality throughout the pitch-uplift cycles, and no grid Reconstruction. In unsteady algorithms, the normal velocity of the interface boundary is constrained to meet the geometric conservation laws under the motion grid. The second-order finite volume format is adopted for the spatial discretization and the implicit time propulsion strategy which combines the two time steps and the BLU-SGS is used for the time discretization. The lift, thrust and energy consumption under different downtimes and different flapping angles are calculated. The mechanism of lift and thrust generation is analyzed. By comparing the aerodynamic force with the flow field, Effect of parameters. The calculation results show that the “static factor” of the airfoil is the main reason for its lift, and the unsteady flow has a positive effect on the increase of the lift force. The aerodynamic performance of the airfoil, such as the downtime and flapping angle, Greater impact. When the current shot time accounts for about 65% -70% of the whole beat cycle, the average lift per hour under the unit energy consumption is the largest, which is consistent with the observed data. In addition, a set of flapping angle parameters with good aerodynamic characteristics were obtained through comparative analysis, which provided reference for the subsequent research on three-dimensional problems.