Zheng Hongyu, Xie Fangfang, Ji Tingwei, Zhu Zaoxu, Zheng Yao
Center for Engineering and Scientific Computation, and School of Aeronautics and Astronautics Zhejiang University, Zhejiang 310027, China.
Phys Rev E. 2020 Jan;101(1-1):013107. doi: 10.1103/PhysRevE.101.013107.
We construct a multifidelity framework for the kinematic parameter optimization of flapping airfoil. We employ multifidelity Gaussian process regression and Bayesian optimization to effectively synthesize the aerodynamic performance of the flapping airfoil with the kinematic parameters under multiresolution numerical simulations. The objective of this work is to demonstrate that the multifidelity framework can efficiently discover the optimal kinematic parameters of the flapping airfoil with specific aerodynamic performance using a limited number of expensive high-fidelity simulations combined with a larger number of inexpensive low-fidelity simulations. We efficiently identify the optimal kinematic parameters of an asymmetrically flapping airfoil with various target aerodynamic forces in the design space of heaving amplitude, flapping frequency, angle of attack amplitude, and stroke angle. Notably, it is found that the angle of attack can significantly affect the magnitude of aerodynamic forces by facilitating the generation of the leading-edge vortex. In the meanwhile, its combination effect with the stroke angle can determine the attitude and trajectory of the flapping airfoil, thus further affect the direction of the aerodynamic forces. With the influence of the streamwise in-line motion, the asymmetrical vortex structures emerge in the wake fields because the streamwise velocities of shedding vortices are different in the upstroke and downstroke. Furthermore, we conduct the kinematic parameter optimization for a three-dimensional asymmetrically flapping wing. Compared to the two-dimensional simulations, we further investigate the flow induced by the vortex ring and its unsteady effects on the vortex structure and aerodynamic performance.
我们构建了一个用于扑翼翼型运动学参数优化的多保真度框架。我们采用多保真度高斯过程回归和贝叶斯优化，在多分辨率数值模拟下有效地将扑翼翼型的空气动力学性能与运动学参数进行综合。这项工作的目的是证明，该多保真度框架可以通过结合大量低成本的低保真模拟和有限数量的高成本的高保真模拟，有效地发现具有特定空气动力学性能的扑翼翼型的最优运动学参数。我们在升沉幅度、扑动频率、攻角幅度和冲程角的设计空间中，有效地识别了具有各种目标空气动力的非对称扑翼翼型的最优运动学参数。值得注意的是，发现攻角可通过促进前缘涡的产生而显著影响空气动力的大小。同时，其与冲程角的组合效应可决定扑翼翼型的姿态和轨迹，进而进一步影响空气动力的方向。受流向直线运动的影响，尾流场中出现非对称涡结构，因为脱落涡在向上冲程和向下冲程中的流向速度不同。此外，我们对三维非对称扑翼进行了运动学参数优化。与二维模拟相比，我们进一步研究了涡环诱导的流动及其对涡结构和空气动力学性能的非定常影响。
