Numerical investigations on the force generation and wake structures of a nonsinusoidal pitching foil
| Autor: | Li-Ming Chao, Dong Zhang, Guo-Xin Yan, Guang Pan |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Physics
Mechanical Engineering Work (physics) Reynolds number 02 engineering and technology Sawtooth wave Mechanics Kinematics Wake Vortex shedding 01 natural sciences 010305 fluids & plasmas symbols.namesake 020303 mechanical engineering & transports 0203 mechanical engineering 0103 physical sciences symbols Symmetry breaking FOIL method |
| Zdroj: | Journal of Fluids and Structures. 85:27-39 |
| ISSN: | 0889-9746 |
| Popis: | We numerically investigate the force generation and wake structures of a nonsinusoidal periodic pitching foil under a thickness-based Reynolds number of R e D = 255 . We consider various nonsinusoidal periodic trajectories of pitching motion, such as the sawtooth and square trajectories, using an adjustable parameter, K . Similar to previous studies on sinusoidal pitching foils, the present results for the nonsinusoidal pitching foil indicate that the transition from a Benard–von Karman wake to a reverse Be nard–von Karman wake precedes the actual drag–thrust transition. In addition, the symmetry breaking of a reverse Be nard–von Karman wake is observed. As K increases, the drag–thrust transition of the nonsinusoidal pitching foil advances gradually and it becomes easy to destabilize the wake structures produced by the oscillating foil. Since K physically describes how rapidly the foil reverses its pitching direction, we argue that the initial velocity of vortex shedding from the foil increases with K and results in the aforementioned phenomena. The present work provides helpful findings for better understanding the kinematic behaviour of actual animals and for designing bio-inspired robotics. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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