Affiliation of Author(s):航空学院
Journal:PHYSICAL REVIEW FLUIDS
Key Words:FISH PERFORMANCE PROPULSION MECHANISM PATTERNS SCHOOLS FLIGHT BIRDS LEADS
Abstract:The effect of phase difference on the collective locomotion of two tandem flapping foils is numerically studied in this paper. The numerical results indicate that the collective locomotion is greatly affected by the phase difference. Two distinct collective modes are observed, i.e., the fast mode and the slow mode. The fast mode is only observed in part of the range of the phase difference (phi), i.e., phi = 0.0-0.1 pi and 1.5 pi-1.9 pi with appropriate initial distance, and the slow mode appears in the range of phi = 0.3 pi-1.4 pi. Meanwhile, the follower of the two foils has hydrodynamic benefit in both fast and slow modes, and it can obtain the highest efficiency in the fast mode at phi = 1.6 pi. However, the leader can only achieve hydrodynamic benefit in the fast mode, and the highest efficiency occurs at phi = 0.1 pi. In addition, the stable distance between two foils in the slow mode can be quantized with the phase difference. Furthermore, the fluid-structure interactions between two foils are also analyzed. Two distinct vortex interactions are observed in the fast mode, i.e., merging interaction and broken interaction, which, respectively, result in the highest propulsive efficiency for the follower and the leader. In the merging interaction, the leading edge vortex of the leader is captured by the follower, which results in the weak trailing edge vortex of the leader but a strong trailing edge vortex of the follower. In the broken interaction, the leading edge vortex of the follower sheds into the wake together with the trailing edge vortex of the leader, and induces the trailing edge vortex of the follower to be broken into two parts. Which kind of vortex interaction occurs depends on the phase difference. The results obtained here may provide some light on understanding the coordinated behavior of biological collectives.
ISSN No.:2469-990X
Translation or Not:no
Date of Publication:2019-05-17
Co-author:Lin, Xingjian,Zhang, Tongwei,Yang, Liming
Correspondence Author:Wu Jie
Date of Publication:2019-05-17