柔性扑翼非定常涡格法气动计算的改进与实现

Implementation of an Improved Unsteady Vortex Lattice Method for Flexible Flapping-wing Aerodynamic Computation

旨在快速、准确地模拟微型扑翼飞行器(Flapping-wing MAV)周边流场,根据柔性扑翼的扑动特点,提出了微型飞行器(MAV)气动力计算的一种改进非定常涡格法(UVLM)模型,该模型中充分考虑机翼的瞬时柔性变形、诱导阻力、尾迹涡环畸变以及黏性耗散等因素对气动力的影响;给出了该模型的一个可视化实现,并通过实例验证了该模型的可行性和有效性。算法仿真表明,采用该模型可使平均升力和平均推力计算精度分别提高20%和70%左右。为了提高运算效率,还研究了剔除尾涡对UVLM性能的影响,计算结果显示,剔除距翼面适当距离处的尾涡后,可在保证算法计算精度基本不下降的前提下使运行时间减少2/3,这表明改进的UVLM可作为MAV的一种快速气动力估算工具,在MAV的优化中存在显见的应用价值。

An improved unsteady vortex lattice method（UVLM） is proposed in this article to simulate the surrounding flow of a flapping-wing micro aerial vehicle（Flapping-wing MAV） precisely which takes into full account the features of the flexible flapping-wing model.The influence of instantaneous wing shape velocity on the aerodynamic forces,the induced drag and the wake stretching as well as dissipation are modeled in this method.And a visual program based on this method is developed.The results are 20% more accurate in lifting coefficient calculation and 70% more accurate in thrust coefficient calculation,which are verified by the computational and experimental data.To further improve the performance of the UVLM,the influence of wake vortex ignoring on time savings and precision is studied.The results show that the savings in central processing unit（CPU） time with wake vortex ignoring could be up to 2/3,which indicates the important value of UVLM in the optimization of flapping-wing vehicle design as a fast aerodynamic approximation method.