当前位置: X-MOL 学术J. Fluids Struct. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Flutter and resonances of a flag near a free surface
Journal of Fluids and Structures ( IF 3.4 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.jfluidstructs.2020.103046
Jérôme Mougel , Sébastien Michelin

Abstract We investigate the effects of a nearby free surface on the stability of a flexible plate in axial flow. Confinement by rigid boundaries is known to affect flag flutter thresholds and fluttering dynamics significantly, and this work considers the effects of a more general confinement involving a deformable free surface. To this end, a local linear stability is proposed for a flag in axial uniform flow and parallel to a free surface, using one-dimensional beam and potential flow models to revisit this classical fluid–structure interaction problem. The physical behaviour of the confining free surface is characterized by the Froude number, corresponding to the ratio of the incoming flow velocity to that of the gravity waves. After presenting the simplified limit of infinite span (i.e. two-dimensional problem), the results are generalized to include finite-span and lateral confinement effects. In both cases, three unstable regimes are identified for varying Froude number. Rigidly-confined flutter is observed for low Froude number, i.e. when the free surface behaves as a rigid wall, and is equivalent to the classical problem of the confined flag. When the flow and wave velocities are comparable, a new instability is observed before the onset of flutter (i.e. at lower reduced flow speed) and results from the resonance of a structural bending wave and one of the fundamental modes of surface gravity waves. Finally, for large Froude number (low effect of gravity), flutter is observed with significant but passive deformation of the free surface in response of the flag’s displacement.

中文翻译:

自由表面附近旗帜的颤动和共振

摘要 我们研究了附近自由表面对轴流中柔性板稳定性的影响。已知刚性边界的限制会显着影响旗帜颤振阈值和颤振动力学,这项工作考虑了涉及可变形自由表面的更一般限制的影响。为此,针对轴向均匀流动中并平行于自由表面的标志提出了局部线性稳定性,使用一维梁和势流模型重新审视这个经典的流固耦合问题。约束自由表面的物理行为由弗劳德数表征,对应于传入流速与重力波的速度之比。给出无限跨度的简化极限后(即二维问题),结果被推广到包括有限跨度和横向限制效应。在这两种情况下,针对不同的弗劳德数确定了三种不稳定状态。在低弗劳德数下观察到刚性约束颤振,即当自由表面表现为刚性壁时,相当于经典的约束旗问题。当流动和波浪速度相当时,在颤振开始之前(即在较低的降低流速下)观察到新的不稳定性,这是由结构弯曲波和表面重力波的基本模式之一的共振引起的。最后,对于大 Froude 数(低重力影响),观察到颤振,自由表面响应标志位移而发生显着但被动的变形。对于不同的弗劳德数,确定了三种不稳定状态。在低弗劳德数下观察到刚性约束颤振,即当自由表面表现为刚性壁时,相当于经典的约束旗问题。当流动和波浪速度相当时,在颤振开始之前(即在较低的降低流速下)观察到新的不稳定性,这是由结构弯曲波和表面重力波的基本模式之一的共振引起的。最后,对于大 Froude 数(低重力影响),观察到颤振,自由表面响应标志位移而发生显着但被动的变形。对于不同的弗劳德数,确定了三种不稳定状态。在低弗劳德数下观察到刚性约束颤振,即当自由表面表现为刚性壁时,相当于经典的约束旗问题。当流动和波浪速度相当时,在颤振开始之前(即在较低的降低流速下)观察到新的不稳定性,这是由结构弯曲波和表面重力波的基本模式之一的共振引起的。最后,对于大 Froude 数(低重力影响),观察到颤振,自由表面响应标志位移而发生显着但被动的变形。等价于经典的受限旗问题。当流动和波浪速度相当时,在颤振开始之前(即在较低的降低流速下)观察到新的不稳定性,这是由结构弯曲波和表面重力波的基本模式之一的共振引起的。最后,对于大 Froude 数(低重力影响),观察到颤振,自由表面响应标志位移而发生显着但被动的变形。等价于经典的受限旗问题。当流动和波浪速度相当时,在颤振开始之前(即在较低的降低流速下)观察到一种新的不稳定性,这是由结构弯曲波和表面重力波的一种基本模式的共振引起的。最后,对于大 Froude 数(低重力影响),观察到颤振,自由表面响应标志位移而发生显着但被动的变形。
更新日期:2020-07-01
down
wechat
bug