Three-dimensional direct numerical simulation of wake transitions of a circular cylinder. (25th July 2016)

• Record Type: Journal Article
• Authors: Jiang, Hongyi; Cheng, Liang; Draper, Scott; An, Hongwei; Tong, Feifei
• Is Part Of: Journal of fluid mechanics. Volume 801(2016:Aug.)
• Page Start: 353
• Page End: 391
• Publication Date: 2016-07-25
• Subjects: vortex instability, -- vortex streets, -- wakes; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2016.446
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : This paper presents three-dimensional (3D) direct numerical simulations (DNS) of flow past a circular cylinder over a range of Reynolds number ( $Re$ ) 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.