Department of Mechanical Engineering, University of Maine, Orono, ME, United States of America.
Bioinspir Biomim. 2017 Dec 13;13(1):016010. doi: 10.1088/1748-3190/aa8447.
In this study, the unsteady flow and acoustic characteristics of a three-dimensional (3D) flapping wing model of a Tibicen linnei cicada in forward-flight are numerically investigated. A single cicada wing is modelled as a membrane with a prescribed motion reconstructed from high-speed videos of a live insect. The numerical solution takes a hydrodynamic/acoustic splitting approach: the flow field is solved with an incompressible Navier-Stokes flow solver based on an immersed boundary method, and the acoustic field is solved with linearized perturbed compressible equations. The 3D simulation allows for the examination of both the directivity and frequency compositions of the flapping wing sound in a full space. Along with the flexible wing model, a rigid wing model that is extracted from real motion is also simulated to investigate the effects of wing flexibility. The simulation results show that the flapping sound is directional; the dominant frequency varies around the wing. The first and second frequency harmonics show different radiation patterns in the rigid and flexible wing cases, which are demonstrated to be highly associated with wing kinematics and loadings. Furthermore, the rotation and deformation in the flexible wing is found to help lower the sound strength in all directions.
在这项研究中，数值研究了一种三维（3D）蝉翼扑动模型在向前飞行中的非定常流动和声学特性。将单个蝉翼建模为膜片，其运动是根据活体昆虫的高速视频重建的。数值解采用了水动力/声学分离方法：流动场通过基于浸入边界法的不可压缩纳维-斯托克斯流求解器求解，而声场通过线性化的可压缩方程求解。3D 模拟允许在全空间中检查扑翼声音的指向性和频率组成。除了柔性翼模型外，还模拟了从真实运动中提取的刚性翼模型，以研究翼的灵活性的影响。模拟结果表明，扑动声是定向的；主导频率在翼周围变化。第一和第二频率谐波在刚性和柔性翼的情况下显示出不同的辐射模式，这被证明与翼的运动学和载荷高度相关。此外，发现柔性翼的旋转和变形有助于降低各个方向的声音强度。
