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Modal and non-modal stabilities of flow around a stack of plates

Theobald, R.; Mao, X.; Jaworski, A.J.; Berson, A.

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Authors

R. Theobald

X. Mao

A.J. Jaworski

A. Berson



Abstract

Modal and non-modal stabilities of flow around a stack of flat plates are investigated by means of asymptotic stability and transient growth analyses respectively. It is observed that over the parameters considered, both the base flow and the stabilities vary as a function of ReW2/(W−1)2, i.e. the product of the Reynolds number and the square of the expansion ratio of the stack. The most unstable modes are found to be located downstream of the recirculation bubble while the global optimal initial perturbations (resulting in maximum energy growth over the entire domain) and the weighted optimal initial perturbations (resulting in maximum energy growth in the close downstream region of the stack) concentrate around the stack end owing to the Orr mechanism. In direct numerical simulations (DNS) of the base flow initially perturbed by the modes, it is noticed that the weighted optimal initial perturbation induces periodic vortex shedding downstream of the stack much faster than the most unstable mode. This observation suggests that the widely reported vortex shedding in flow around a stack of plates, e.g. in thermoacoustic devices, is associated with perturbations around the stack end.

Citation

Theobald, R., Mao, X., Jaworski, A., & Berson, A. (2015). Modal and non-modal stabilities of flow around a stack of plates. European Journal of Mechanics - B/Fluids, 53, 113-118. https://doi.org/10.1016/j.euromechflu.2015.04.005

Journal Article Type Article
Acceptance Date Apr 14, 2015
Publication Date Sep 1, 2015
Deposit Date Apr 23, 2015
Publicly Available Date Apr 23, 2015
Journal European Journal of Mechanics - B/Fluids
Print ISSN 0997-7546
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 53
Pages 113-118
DOI https://doi.org/10.1016/j.euromechflu.2015.04.005
Keywords Laminar wake, Flat plates, Stability.

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