# Publication: Three-dimensional Floquet stability analysis of the wake in cylinder arrays

All || By Area || By YearTitle | Three-dimensional Floquet stability analysis of the wake in cylinder arrays |
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Authors/Editors* | N. K.-R. Kevlahan |

Where published* | Journal of Fluid Mechanics |

How published* | Journal |

Year* | 2007 |

Volume | 592 |

Number | |

Pages | 79-88 |

Publisher | Cambridge University Press |

Keywords | tube arrays, Floquet stability analysis, fluid-structure interaction |

Link | http://journals.cambridge.org/download.php?file=%2FFLM%2FFLM592%2FS0022112007008798a.pdf&code=434d72092347ab33892e95a86818a91c |

Abstract |
Three-dimensional stability of the periodic wake of tightly packed rotated and inline cylinder arrays is investigated for 60<=Re<=270. Results are compared with existing numerical and experimental studies for an isolated cylinder. Numerical Floquet analysis shows that the two-dimensional wakes of the rotated and inline arrays with spacing P/D=1.5 become unstable at Re_c = 64+/-0.5 and Re_c = 132+/-1 respectively. Two-dimensional vortex shedding flow is unlikely in practice for such flows. The dominant spanwise wavelength is lambda/D=0.9+/-0.1 for the rotated array at Re=100 and lambda/D = 3.0 +/- 0.1 for the inline array at Re=200. Three-dimensional simulations show excellent agreement with the Floquet analysis for the rotated case, and reasonable agreement for the inline case. The instability mechanism appears to be similar to Mode A for an isolated cylinder, although the structure of the three-dimensional vorticity is different due to the spatial periodicity of the flow. Unlike the isolated cylinder, both array flows are unstable as lambda tends to infinity (like a thin shear layer). This is the first investigation of three-dimensional wake instability in cylinder arrays, a problem of significant practical and theoretical interest. |

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