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Abstract
A stable three-dimensional (3D) wake structure for flow past a circular cylinder has been discovered through 3D direct numerical simulations (DNS). The stable 3D wake structure occurs over a small range of Reynolds number (Re) below the critical Re for Mode A* (i.e., Mode A with large-scale vortex dislocations, where Mode A is the first 3D instability mode which will evolve into Mode A*) instability. It is believed that the stable 3D wake structure discovered in this study is the stable state of Mode A wake structure inferred by Williamson ["Three-dimensional wake transition," J. Fluid Mech. 328, 345-407 (1996)]. This confirms the wake transition sequence of 2D → A → A* → B suggested byWilliamson. Compared with conventional Mode A structure, the stable state of Mode A structure has much weaker amplitude and does not evolve into large-scale vortex dislocations. The stable state of Mode A structure is triggered by small-scale spanwise disturbance introduced upstream of the cylinder, due to energy amplification through convective instability of the flow. The stable state of Mode A is transient and is damped out eventually under a transient initial disturbance condition, but is sustained throughout under a persistent disturbance condition. The emergence of the stable state of Mode A structure is correlated with both Re and the disturbance level. With the decrease of Re, the stable state of Mode A structure gradually becomes less well-defined and eventually disappears. With the decrease of the disturbance level, the stable state of Mode A structure emerges at a higher Re.
Original language | English |
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Article number | 104103 |
Pages (from-to) | 104103-1 to 104103-13 |
Number of pages | 13 |
Journal | Physics of Fluids |
Volume | 28 |
Issue number | 10 |
DOIs | |
Publication status | Published - 1 Oct 2016 |
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Dive into the research topics of 'Stable state of mode A for flow past a circular cylinder'. Together they form a unique fingerprint.Projects
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Effect of natural seabed on hydrodynamics around cylindrical structures
An, H. (Investigator 01)
ARC Australian Research Council
1/01/15 → 11/01/18
Project: Research