Hostname: page-component-848d4c4894-wg55d Total loading time: 0 Render date: 2024-05-12T00:22:38.980Z Has data issue: false hasContentIssue false
  • English
  • Français

Flapping of heavy inverted flags: a fluid-elastic instability

Published online by Cambridge University Press:  13 October 2020

Mohammad Tavallaeinejad Open the ORCID record for Mohammad Tavallaeinejad [Opens in a new window] ,
Michael P. Païdoussis Open the ORCID record for Michael P. Païdoussis [Opens in a new window] ,
Manuel Flores Salinas ,
Mathias Legrand ,
Mojtaba Kheiri  and
Ruxandra M. Botez
Mohammad Tavallaeinejad
Affiliation:
Department of Mechanical Engineering, McGill University, Montréal, Québec, CanadaH3A 0C3
Michael P. Païdoussis*
Affiliation:
Department of Mechanical Engineering, McGill University, Montréal, Québec, CanadaH3A 0C3
Manuel Flores Salinas
Affiliation:
Laboratoire de Recherche en Commande Active, Avionique et Aéroservoélasticité, École de Technologie Supérieure, Montréal, Québec, CanadaH3C 6M8
Mathias Legrand
Affiliation:
Department of Mechanical Engineering, McGill University, Montréal, Québec, CanadaH3A 0C3
Mojtaba Kheiri
Affiliation:
Department of Mechanical, Industrial and Aerospace Engineering, Concordia University, Montréal, Québec, CanadaH3G 1M8
Ruxandra M. Botez
Affiliation:
Laboratoire de Recherche en Commande Active, Avionique et Aéroservoélasticité, École de Technologie Supérieure, Montréal, Québec, CanadaH3C 6M8
*
†Email address for correspondence: michael.paidoussis@mcgill.ca
Get access Rights & Permissions [Opens in a new window]

Abstract

Wind tunnel experiments are described in this paper, aiming to examine the global dynamics of heavy inverted flags, with a specific focus on the underlying mechanism of large-amplitude flapping, which occurs at sufficiently high flow velocities. This problem is of interest because no consensus exists as to the mechanism, specifically whether it is a vortex-induced vibration or a self-excited vibration – the answer being not only of fundamental interest, but also important for energy harvesting applications. The effect of vortex shedding from both leading and trailing edges was investigated via experiments with flags modified by serrations to the leading edge and a long rigid splitter plate at the trailing edge, so as to disrupt leading- and trailing-edge vortices and to inhibit interactions between counter-rotating leading-edge vortices, if they exist. The relatively small quantitative changes in the critical flow velocity, amplitude and frequency of oscillations, as well as the near-identical qualitative behaviour, of plain and modified flags suggests that the global qualitative dynamics of heavy inverted flags is independent of vortex shedding from the leading and trailing edges, i.e. periodic vortex shedding is not the cause but an effect of large-amplitude flapping. Additional experiments showed that the dominant frequencies of flapping and the lift force on the flag are generally not synchronized, and multiple frequencies occur in the lift signal, reinforcing the conclusion that vortex shedding is not the cause of flapping. Our experimental results suggest that self-excited vibration through a fluid-elastic instability, i.e. flutter, is the underlying mechanism for the flapping of heavy inverted flags.

Type
JFM Rapids
Information
Journal of Fluid Mechanics , Volume 904 , 10 December 2020 , R5
Check for updates
Copyright
© The Author(s), 2020. Published by Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Goza, A., Colonius, T. & Sader, J. E. 2018 Global modes and nonlinear analysis of inverted-flag flapping. J. Fluid Mech. 857, 312–344.CrossRefGoogle Scholar
Gurugubelli, P. S. & Jaiman, R. K. 2015 Self-induced flapping dynamics of a flexible inverted foil in a uniform flow. J. Fluid Mech. 781, 657–694.CrossRefGoogle Scholar
Gurugubelli, P. S. & Jaiman, R. K. 2017 On the mechanism of large amplitude flapping of inverted foil in a uniform flow. arXiv:1711.01065.Google Scholar
Gurugubelli, P. S. & Jaiman, R. K. 2019 Large amplitude flapping of an inverted elastic foil in uniform flow with spanwise periodicity. J. Fluids Struct. 90, 139–163.CrossRefGoogle Scholar
Khalak, A. & Williamson, C. H. 1999 Motions, forces and mode transitions in vortex-induced vibrations at low mass-damping. J. Fluids Struct. 13 (7–8), 813–851.CrossRefGoogle Scholar
Kim, D., Cossé, J., Huertas Cerdeira, C. & Gharib, M. 2013 Flapping dynamics of an inverted flag. J. Fluid Mech. 736, R1.CrossRefGoogle Scholar
Konstantinidis, E., Zhao, J., Jacono, D. L., Leontini, J. & Sheridan, J. 2019 Phase dynamics of effective drag and lift in vortex-induced vibration at low mass-damping. Preprint.CrossRefGoogle Scholar
Naudascher, E. & Rockwell, D. 1994 Flow-Induced Vibrations: An Engineering Guide. A.A. Balkema.Google Scholar
Nemes, A., Zhao, J., Jacono, D. L. & Sheridan, J. 2012 The interaction between flow-induced vibration mechanisms of a square cylinder with varying angles of attack. J. Fluid Mech. 710, 102–130.CrossRefGoogle Scholar
Pazhani, K. M. 2018 An experimental investigation of the dynamics of an inverted serrated flag. PhD thesis, Illinois Institute of Technology.Google Scholar
Ryu, J., Park, S. G., Kim, B. & Sung, H. J. 2015 Flapping dynamics of an inverted flag in a uniform flow. J. Fluids Struct. 57, 159–169.CrossRefGoogle Scholar
Sader, J. E., Cossé, J., Kim, D., Fan, B. & Gharib, M. 2016 Large-amplitude flapping of an inverted flag in a uniform steady flow – a vortex-induced vibration. J. Fluid Mech. 793, 524–555.CrossRefGoogle Scholar
Seyed-Aghazadeh, B., Carlson, D. W. & Modarres-Sadeghi, Y. 2017 Vortex-induced vibration and galloping of prisms with triangular cross-sections. J. Fluid Mech. 817, 590–618.CrossRefGoogle Scholar
Tavallaeinejad, M. 2020 Nonlinear dynamics of inverted flags: a theoretical and experimental investigation. PhD thesis, McGill University.Google Scholar
Tavallaeinejad, M., Legrand, M. & Païdoussis, M. P. 2020 a Nonlinear dynamics of slender inverted flags in uniform steady flows. J. Sound Vib. 467, 115048.CrossRefGoogle Scholar
Tavallaeinejad, M., Païdoussis, M. P., Legrand, M. & Kheiri, M. 2020 b Instability and the post-critical behaviour of two-dimensional inverted flags in axial flow. J. Fluid Mech. 890, A14.CrossRefGoogle Scholar
Yu, Y., Liu, Y. & Chen, Y. 2017 Vortex dynamics behind a self-oscillating inverted flag placed in a channel flow: time-resolved particle image velocimetry measurements. Phys. Fluids 29 (12), 125104.CrossRefGoogle Scholar
Zhao, J., Leontini, J., Lo Jacono, D. & Sheridan, J. 2014 Fluid–structure interaction of a square cylinder at different angles of attack. J. Fluid Mech. 747, 688–721.CrossRefGoogle Scholar