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基于高阶谱差分(SD)格式的高成本效益的优化方法被用以优化扑翼面的运动学,从而达到最大推进效率。具体来说,基于梯度的优化算法与高阶谱差分的纳维-斯托克斯流动求解器被耦合用以研究一系列NACA对称翼型的最优运动学。在此研究中,翼型做沉标和俯仰运动。数值优化在粗网格上进行。得到最优解后,在密网格上用高阶SD求解器捕获处于最优运动学状态下扑翼面的详细涡结构。提出的数值优化框架被用以研究翼型厚度,雷诺数和俯仰中心位置对最佳巡航飞行的影响。通过研究相关流场,气动力以及等效攻角(AOA)的变化,我们解释了与最佳扑翼面运动相关的流动物理特性。
A cost-effective optimization method based on the high-order spectral difference (SD) format is used to optimize the kinematics of the flapping wing to achieve maximum propulsion efficiency. Specifically, a gradient-based optimization algorithm and a higher order spectral difference Navier-Stokes flow solver are coupled to study the optimal kinematics of a series of NACA symmetric airfoils. In this study, airfoils were used for sink marks and pitch movements. Numerical optimization is done on a coarse grid. After getting the optimal solution, the detailed vortex structure of flapping wing surface under optimal kinematics is captured by a high-order SD solver on a dense grid. The proposed numerical optimization framework is used to study the effect of airfoil thickness, Reynolds number, and pitch center location on the best cruise flight. By studying the pertinent flow field, aerodynamic forces, and changes in the AOA, we explain the flow physics associated with optimal flapping airfoil motion.