Abstract
As is known, the maximum thickness position plays a key role in determining the energy extraction properties for flapping wing airfoils. Previous work demonstrated that the energy extraction efficiency might increase when we move the maximum thickness position towards the leading-edge direction. Inspired from this phenomenon, we propose in this work the addition of a flat plate at the tail of the flapping wings. Under two different Reynolds numbers (Re = 1100 and Re = 5×105), the effect of adding a rigid flat plate or a flexible flat plate to the trailing edge of the flapping wing on the flapping wing’s energy efficiency was investigated. The corresponding results were also compared with that of the original flapping wing. Results show that the addition of a rigid flat plate is sufficient for the amelioration of the flapping wing’s energy extraction efficiency in low Reynolds number cases. At high Reynolds number cases, the flapping wing with flexible flat plate trailing edge can maintain a relatively high energy extraction efficiency over a wide range of frequency, while the flapping wing with rigid flat plate trailing edge can only improve the energy extraction efficiency in the low frequency region. Therefore, we propose the application of flapping wings with flexible flat plate trailing edge for increasing the energy extraction efficiency under high Reynolds number conditions.
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Abbreviations
- C :
-
Chord length of airfoil
- C y :
-
Heaving force coefficient in vertical direction
- C m :
-
Pitching moment coefficient
- C py :
-
Energy extraction coefficient of heaving motion
- C pθ :
-
Energy extraction coefficient of pitching motion
- C ps :
-
Surface pressure coefficient
- C p :
-
Overall energy extraction coefficient
- f* :
-
Dimensionless oscillation frequency
- Ht :
-
The trailing edge deformation size
- θ 0 :
-
Pitch angle amplitude
- Re :
-
Reynolds number
- V y :
-
Translational speed in the y direction
- X p :
-
Location of pitch axis
- X d :
-
Location of maximum thickness position
- η :
-
Energy extraction efficiency of the flapping wing
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Acknowledgments
This work was supported by National Natural Science Foundation of China Grants (No. 91852117 and 51576131).
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Longfeng Hou is a researcher at the School of Energy and Power Engineering in the University of Shanghai for Science and Technology. He received his Ph.D. in Thermal Engineering from INSA LYON. His research interests include fluid mechanics, radiative heat transfer.
Pu Yang is a graduate student at the School of Energy and Power Engineering in the University of Shanghai for Science and Technology. He received his Master’s from the University of Shanghai for Science and Technology. His research interest is focused on fluid mechanics.
Dongmei Du is a Senior Engineer in the Science and Technology on Water Jet Propulsion Laboratory of Marine and Research Institute of China. Her research interest is about water jet propulsion technology.
Bing Zhu is a researcher at the School of Energy and Power Engineering in the University of Shanghai for Science and Technology. He received his Ph.D. in Thermal Engineering from University of Shanghai. His research interests include numerical simulation of flow, flow control, new energy conversion device, fluid machinery.
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Hou, L., Yang, P., Du, D. et al. An adaptive plate at flapping wing’s trailing edge in promoting energy extraction performance. J Mech Sci Technol 35, 591–600 (2021). https://doi.org/10.1007/s12206-021-0119-x
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DOI: https://doi.org/10.1007/s12206-021-0119-x