Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry
The performance augmentation mechanism of a tandem-foil system undergoing time-asymmetric flapping with unequal up- and downstroke durations (velocities) is investigated at three different phase angles, 0°, 90°, and 180°. Specifically, an asymmetry ratio, ranging from 0 to 0.4, is introduced to quan...
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sg-ntu-dr.10356-1541142022-02-18T06:02:49Z Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry Wang, Guangjian Ng, Bing Feng Teo, Zhen Wei Lua, Kim Boon Bao, Yan School of Mechanical and Aerospace Engineering Singapore Centre for 3D Printing Engineering::Mechanical engineering Tandem Flapping Foils Stroke Time-Asymmetry The performance augmentation mechanism of a tandem-foil system undergoing time-asymmetric flapping with unequal up- and downstroke durations (velocities) is investigated at three different phase angles, 0°, 90°, and 180°. Specifically, an asymmetry ratio, ranging from 0 to 0.4, is introduced to quantify the degree of the stroke time-asymmetry and to serve as the primary kinematic parameter of interest that affects the foil performances. Numerical simulations are implemented to predict the force production and to investigate the associated mechanism at different asymmetry ratios and phase angles. Validations are performed using digital particle image velocimetry in water tunnel experiments with two identical 3D printed wings. The results suggest that the foil performances at proper phase angles can be enhanced by stroke time-asymmetry. The force production during in-phase flapping obtains 15% increment while that during counterstroke flapping achieves remarkable enhancements by 2.5 times, as the asymmetry ratio increases from 0 to 0.4. The study also demonstrates that such enhancements are achieved through the changes in foil flapping velocities and foil-vortex interactions between the unequal up- and downstrokes. These findings not only provide insights toward the characteristics of tandem foils which are operated in non-sinusoidal flapping strokes but also offer a reference to the design of efficient wing kinematics for high-performance biomimetic propulsors. National Research Foundation (NRF) Accepted version The authors would like to thank the Singapore Centre for 3D Printing, which is supported by the National Research Foundation, Prime Minister’s Office, Singapore under its Medium-Sized Centre funding scheme, as well as the support from Nanyang Technological University through grant no. 04INS000329C160 and 04INS000453C160. 2021-12-15T09:01:28Z 2021-12-15T09:01:28Z 2021 Journal Article Wang, G., Ng, B. F., Teo, Z. W., Lua, K. B. & Bao, Y. (2021). Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry. Aerospace Science and Technology, 117, 106939-. https://dx.doi.org/10.1016/j.ast.2021.106939 1270-9638 https://hdl.handle.net/10356/154114 10.1016/j.ast.2021.106939 2-s2.0-85109832970 117 106939 en 04INS000329C160 04INS000453C160 Aerospace Science and Technology © 2021 Elsevier Masson SAS. All rights reserved. This paper was published in Aerospace Science and Technology and is made available with permission of Elsevier Masson SAS. application/pdf |
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Engineering::Mechanical engineering Tandem Flapping Foils Stroke Time-Asymmetry Wang, Guangjian Ng, Bing Feng Teo, Zhen Wei Lua, Kim Boon Bao, Yan Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
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The performance augmentation mechanism of a tandem-foil system undergoing time-asymmetric flapping with unequal up- and downstroke durations (velocities) is investigated at three different phase angles, 0°, 90°, and 180°. Specifically, an asymmetry ratio, ranging from 0 to 0.4, is introduced to quantify the degree of the stroke time-asymmetry and to serve as the primary kinematic parameter of interest that affects the foil performances. Numerical simulations are implemented to predict the force production and to investigate the associated mechanism at different asymmetry ratios and phase angles. Validations are performed using digital particle image velocimetry in water tunnel experiments with two identical 3D printed wings. The results suggest that the foil performances at proper phase angles can be enhanced by stroke time-asymmetry. The force production during in-phase flapping obtains 15% increment while that during counterstroke flapping achieves remarkable enhancements by 2.5 times, as the asymmetry ratio increases from 0 to 0.4. The study also demonstrates that such enhancements are achieved through the changes in foil flapping velocities and foil-vortex interactions between the unequal up- and downstrokes. These findings not only provide insights toward the characteristics of tandem foils which are operated in non-sinusoidal flapping strokes but also offer a reference to the design of efficient wing kinematics for high-performance biomimetic propulsors. |
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School of Mechanical and Aerospace Engineering |
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School of Mechanical and Aerospace Engineering Wang, Guangjian Ng, Bing Feng Teo, Zhen Wei Lua, Kim Boon Bao, Yan |
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Article |
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Wang, Guangjian Ng, Bing Feng Teo, Zhen Wei Lua, Kim Boon Bao, Yan |
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Wang, Guangjian |
title |
Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
title_short |
Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
title_full |
Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
title_fullStr |
Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
title_full_unstemmed |
Performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
title_sort |
performance augmentation mechanism of tandem flapping foils with stroke time-asymmetry |
publishDate |
2021 |
url |
https://hdl.handle.net/10356/154114 |
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1725985711464644608 |