How flexibility affects the wake symmetry properties of a self-propelled plunging foil

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	How flexibility affects the wake symmetry properties of a self-propelled plunging foil
	Zhu XJ(朱晓珏); He GW(何国威); Zhang X(张星)
刊名	Journal of Fluid Mechanics
	2014-07
通讯作者邮箱	zhangx@lnm.imech.ac.cn
卷号	751 页码:164-183.
关键词	flow-structure interactions propulsion vortex streets
ISSN号	0022-1120
通讯作者	张星
英文摘要	The wake symmetry properties of a flapping-foil system are closely associated with its propulsive performance. In the present work, the effect of the foil flexibility on the wake symmetry properties of a self-propelled plunging foil is studied numerically. We compare the wakes of a flexible foil and a rigid foil at a low flapping Reynolds number of 200. The two foils are of the same dimensions, flapping frequency, leading-edge amplitude and cruising velocity but different bending rigidities. The results indicate that flexibility can either inhibit or trigger the symmetry breaking of the wake. We find that there exists a threshold value of vortex circulation above which symmetry breaking occurs. The modification of vortex circulation is found to be the pivotal factor in the influence of the foil flexibility on the wake symmetry properties. An increase in flexibility can result in a reduction in the vorticity production at the leading edge because ofthe decrease in the effective angle of attack, but it also enhances vorticity production at the trailing edge because of the increase in the trailing-edge flapping velocity. The competition between these two opposing effects eventually determines the strength of vortex circulation, which, in turn, governs the wake symmetry properties. Further investigation indicates that the former effect is related to the streamlined shape of the deformed foil while the latter effect is associated with structural resonance. The results of this work provide new insights into the functional role of passive flexibility inflapping-based biolocomotion.
学科主题	流体力学
分类号	一类
收录类别	SCI ; EI
资助信息	NSFC: 11021262, 11023001, 11232011,11372331. 973: 2013CB834100
原文出处	http://dx.doi.org/10.1017/jfm.2014.310
语种	英语
WOS记录号	WOS:000337925000011
公开日期	2014-06-19
内容类型	期刊论文
源URL	[http://dspace.imech.ac.cn/handle/311007/48856]
专题	力学研究所_非线性力学国家重点实验室
推荐引用方式 GB/T 7714	Zhu XJ,He GW,Zhang X. How flexibility affects the wake symmetry properties of a self-propelled plunging foil[J]. Journal of Fluid Mechanics,2014,751:164-183..
APA	Zhu XJ,He GW,&Zhang X.(2014).How flexibility affects the wake symmetry properties of a self-propelled plunging foil.Journal of Fluid Mechanics,751,164-183..
MLA	Zhu XJ,et al."How flexibility affects the wake symmetry properties of a self-propelled plunging foil".Journal of Fluid Mechanics 751(2014):164-183..