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Effect of perforation on flow past a conic cylinder at Re=100:vortex-shedding pattern and force history

Acta Mechanica Sinica 2018年第2期34卷 238-256页

作者： L.M.Lin X.F.Zhong Y.X.Wu Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences

The flow past a circular-section cylinder with a conic shroud perforated with four holes at the peak was simulated numerically at Re = 100, considering two factors, *** angle of attack and the diameter of the holes. The effects of the perforated conic shroud on the vortex shedding pattern in the near wake was mainly investigated, as well as the time history of the drag and lift forces. In the investigated parameter space, three flow regimes were generally identified, corresponding to weak, moderate, and strong disturbance *** regime I, the wake can mainly be described by alternately shedding Kármán or Kármán-like vortices. In regime II, the spanwise vortices are obviously disturbed along the span due to the appearance of additional vorticity components and their interactions with the spanwise vortices, but still shed in synchronization along the spanwise direction. In regime III,the typical Kármán vortices partially or totally disappear,and some new vortex shedding patterns appear, such as-type, obliquely shedding, and crossed spanwise vortices with opposite sign. Corresponding to these complex vortex shedding patterns in the near wake, the fluid forces no longer oscillate regularly at a single vortex shedding frequency, but rather with a lower modulation frequency and multiple amplitudes. An overview of these flow regimes is presented.

关键词： vortex shedding pattern Fluid forces Flow control Conical shroud Perforation

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Numerical simulation of flow interference between four cylinders in in-line square arrangement

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Journal of Harbin Institute of Technology(New Series) 2011年第1期18卷 113-120页

作者：徐枫欧进萍肖仪清 School of Civil Engineering Harbin Institute of Technology School of Civil & Hydraulic Engineering Dalian University of Technology Shenzhen Graduate School Harbin Institute of Technology

In the present paper,two-and three-dimensional numerical simulations of the flow interference between four cylinders in an in-line square arrangement at Re = 200 are *** with the two-dimensional(2-D) numerical simulation,the mean and fluctuating forces,Strouhal number(St) and vortex shedding pattern in the wake for each cylinder were analyzed with the spacing ratio(L /D) ranging from 1.5 to *** was found that,four different vortex modes(viz.,flip-flopping,shielding anti-phase-synchronized,in-phasesynchronized and anti-phase-synchronized) gradually appear with the increase of the L/D *** average drag coefficient of the upstream cylinders is larger than that of the downstream cylinders,while the downstream cylinders usually undergo serious fluctuating *** the L/D ratio ranges from 3.0 to 4.0,the dominant frequency of the drag coefficient is equal to the value of St of upstream *** indicates that a simultaneous resonance in the in-flow and cross-flow directions may occur for some single structures of a multi-body oscillating *** the 3-D numerical simulation,the L/D and aspect ratios are kept constant as 5.0 and 10,*** was found that some vortices are formed in the wake of the upstream ***,with the same spacing ratio,the calculated drag coefficient and lift coefficient fluctuation are slightly larger than the 2-D results,but with a phase difference.

关键词： four cylinders vortex shedding pattern flow interference simultaneous resonance three-dimensional numerical simulation

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