Effects of time-varying flexibility on the propulsion performance of a flapping foil

Guangyu Shi; Qing Xiao; Qiang Zhu

doi:10.1063/5.0027927

Propulsion Performance of the Full-Active Flapping Foil in Time-Varying Freestream

Applied Sciences ◽

10.3390/app10186226 ◽

2020 ◽

Vol 10 (18) ◽

pp. 6226

Author(s):

Zhanfeng Qi ◽

Lishuang Jia ◽

Yufeng Qin ◽

Jian Shi ◽

Jingsheng Zhai

Keyword(s):

Flow Velocity ◽

Steady Flow ◽

Navier Stokes ◽

Time Varying ◽

Flapping Foil ◽

Propulsion Performance ◽

Reduced Frequency ◽

Motion Parameters ◽

Volume Method ◽

The Impact

A numerical investigation of the propulsion performance and hydrodynamic characters of the full-active flapping foil under time-varying freestream is conducted. The finite volume method is used to calculate the unsteady Reynolds averaged Navier–Stokes by commercial Computational Fluid Dynamics (CFD) software Fluent. A mesh of two-dimensional (2D) NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first investigate the propulsion performance of the flapping foil in the parameter space of reduced frequency and pitching amplitude at a uniform flow velocity. We define the time-varying freestream as a superposition of steady flow and sinusoidal pulsating flow. Then, we study the influence of time-varying flow velocity on the propulsion performance of flapping foil and note that the influence of the time-varying flow is time dependent. For one period, we find that the oscillating amplitude and the oscillating frequency coefficient of the time-varying flow have a significant influence on the propulsion performance of the flapping foil. The influence of the time-varying flow is related to the motion parameters (reduced frequency and pitching amplitude) of the flapping foil. The larger the motion parameters, the more significant the impact of propulsion performance of the flapping foil. For multiple periods, we note that the time-varying freestream has little effect on the propulsion performance of the full-active flapping foil at different pitching amplitudes and reduced frequency. In summary, we conclude that the time-varying incoming flow has little effect on the flapping propulsion performance for multiple periods. We can simplify the time-varying flow to a steady flow field to a certain extent for numerical simulation.

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Effects of Regular Waves on Propulsion Performance of Flexible Flapping Foil

Applied Sciences ◽

10.3390/app8060934 ◽

2018 ◽

Vol 8 (6) ◽

pp. 934 ◽

Cited By ~ 3

Author(s):

Peng Liu ◽

Yebao Liu ◽

Shuling Huang ◽

Jianfeng Zhao ◽

Yumin Su

Keyword(s):

Regular Waves ◽

Flapping Foil ◽

Propulsion Performance

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Effects of time-varying camber deformation on flapping foil propulsion and power extraction

Journal of Fluids and Structures ◽

10.1016/j.jfluidstructs.2015.05.001 ◽

2015 ◽

Vol 56 ◽

pp. 152-176 ◽

Cited By ~ 21

Author(s):

C.M. Hoke ◽

J. Young ◽

J.C.S. Lai

Keyword(s):

Time Varying ◽

Power Extraction ◽

Flapping Foil

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The Effect of Mass Ratio and Damping Coefficient on the Propulsion Performance of the Semi-Active Flapping Foil of the Wave Glider

Journal of Marine Science and Engineering ◽

10.3390/jmse8050303 ◽

2020 ◽

Vol 8 (5) ◽

pp. 303

Author(s):

Zhanfeng Qi ◽

Min Jiang ◽

Lishuang Jia ◽

Bo Zou ◽

Jingsheng Zhai

Keyword(s):

Output Power ◽

Damping Coefficient ◽

Power Coefficient ◽

Mass Ratio ◽

Propulsion Efficiency ◽

Flapping Foil ◽

Propulsion Performance ◽

Reduced Frequency ◽

The Mean ◽

Wave Glider

A numerical investigation on the propulsion performance of the semi-active flapping foil of the wave glider with different mass ratio and damping coefficient is investigated. The commercial CFD software Fluent is used to solve the URANS equations around the flapping foil by the Finite Volume Method. A mesh of 2D NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first analyze the effect of the mass ratio on the mean output power coefficient and propulsion efficiency and note that with the variation of the mass ratio, the propulsion efficiency decreases slightly. Besides, we find that the mass ratio has a noticeable influence on the mean output power coefficient, and the influence is determined by the reduced frequency. For high reduced frequency, with the increase of the mass ratio, the propulsion performance of the flapping foil decreases monotonously. For low reduced frequency, the mean output power increases slightly. For critically reduced frequency, the mean output power coefficient of the foil firstly increases and then decreases via the mass ratio increase. Then, we examine the influence of the damping coefficient on the propulsion performance of the flapping foil and find that the damping coefficient has a severe adverse effect on the output power and propulsion efficiency. We conclude that the influence of the damping coefficient should be considered first when we design the propulsion device of the semi-active flapping foil. Meanwhile, we should also consider the sea conditions to choose the mass ratio to optimize the flapping foil.

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