### Abstract

This paper presents three-dimensional (3D) direct numerical simulations (DNS) of flow past a circular cylinder over a range of Reynolds number up to 300. The gradual wake transition process from mode A∗ (i.e. mode A with large-scale vortex dislocations) to mode B is well captured over a range of Re from 230 to 260. The mode swapping process is investigated in detail with the aid of numerical flow visualization. It is found that the mode B structures in the transition process are developed based on the streamwise vortices of mode A or A∗ which destabilize the braid shear layer region. For each case within the transition range, the transient mode swapping process consists of dislocation and non-dislocation cycles. With the increase of Re, it becomes more difficult to trigger dislocations from the pure mode A structure and form a dislocation cycle, and each dislocation stage becomes shorter in duration, resulting in a continuous decrease in the probability of occurrence of mode A∗ and a continuous increase in the probability of occurrence of mode B. The occurrence of mode A∗ results in a relatively strong flow three-dimensionality. A critical condition is confirmed at approximately Re = 265-270, where the weakest flow three-dimensionality is observed, marking a transition from the disappearance of mode A∗ to the emergence of increasingly disordered mode B structures.

Original language | English |
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Pages (from-to) | 353-391 |

Journal | Journal of Fluid Mechanics |

Volume | 801 |

Early online date | 25 Jul 2016 |

DOIs | |

Publication status | Published - Aug 2016 |

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**Three-dimensional direct numerical simulation of wake transitions of a circular cylinder.** / Jiang, Hongyi; Cheng, Liang; Draper, Scott; An, Hongwei; Tong, Feifei.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Three-dimensional direct numerical simulation of wake transitions of a circular cylinder

AU - Jiang, Hongyi

AU - Cheng, Liang

AU - Draper, Scott

AU - An, Hongwei

AU - Tong, Feifei

PY - 2016/8

Y1 - 2016/8

N2 - © 2016 Cambridge University Press.This paper presents three-dimensional (3D) direct numerical simulations (DNS) of flow past a circular cylinder over a range of Reynolds number up to 300. The gradual wake transition process from mode A∗ (i.e. mode A with large-scale vortex dislocations) to mode B is well captured over a range of Re from 230 to 260. The mode swapping process is investigated in detail with the aid of numerical flow visualization. It is found that the mode B structures in the transition process are developed based on the streamwise vortices of mode A or A∗ which destabilize the braid shear layer region. For each case within the transition range, the transient mode swapping process consists of dislocation and non-dislocation cycles. With the increase of Re, it becomes more difficult to trigger dislocations from the pure mode A structure and form a dislocation cycle, and each dislocation stage becomes shorter in duration, resulting in a continuous decrease in the probability of occurrence of mode A∗ and a continuous increase in the probability of occurrence of mode B. The occurrence of mode A∗ results in a relatively strong flow three-dimensionality. A critical condition is confirmed at approximately Re = 265-270, where the weakest flow three-dimensionality is observed, marking a transition from the disappearance of mode A∗ to the emergence of increasingly disordered mode B structures.

AB - © 2016 Cambridge University Press.This paper presents three-dimensional (3D) direct numerical simulations (DNS) of flow past a circular cylinder over a range of Reynolds number up to 300. The gradual wake transition process from mode A∗ (i.e. mode A with large-scale vortex dislocations) to mode B is well captured over a range of Re from 230 to 260. The mode swapping process is investigated in detail with the aid of numerical flow visualization. It is found that the mode B structures in the transition process are developed based on the streamwise vortices of mode A or A∗ which destabilize the braid shear layer region. For each case within the transition range, the transient mode swapping process consists of dislocation and non-dislocation cycles. With the increase of Re, it becomes more difficult to trigger dislocations from the pure mode A structure and form a dislocation cycle, and each dislocation stage becomes shorter in duration, resulting in a continuous decrease in the probability of occurrence of mode A∗ and a continuous increase in the probability of occurrence of mode B. The occurrence of mode A∗ results in a relatively strong flow three-dimensionality. A critical condition is confirmed at approximately Re = 265-270, where the weakest flow three-dimensionality is observed, marking a transition from the disappearance of mode A∗ to the emergence of increasingly disordered mode B structures.

U2 - 10.1017/jfm.2016.446

DO - 10.1017/jfm.2016.446

M3 - Article

VL - 801

SP - 353

EP - 391

JO - Journal of Fluid Mechanics.

JF - Journal of Fluid Mechanics.

SN - 0022-1120

ER -