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DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder: (pure) mode A
Lin LM(林黎明); Tan ZR
AbstractIn the present paper, the spatio-temporal evolution of vorticity in the first wake instability, i.e., (pure) mode A, is investigated in order to understand the wake vortex dynamics and sign relationships among vorticity components. Direct numerical simulation (DNS) for the flow past a circular cylinder is performed, typically at a Reynolds number of 200, in the three-dimensional (3-D) wake transition. According to characteristics of time histories of fluid forces, three different stages are identified as the computational transition, the initial stage and fully developed wake. In the second initial stage, the original two-dimensional spanwise vortices become obviously three-dimensional associated with the streamwise or vertical vorticity intensified up to about 0.1. As a matter of fact, these additional vorticities, caused by the intrinsic 3-D instability, are already generated firstly on cylinder surfaces early in the computational transition, indicating that the three-dimensionality appeared early near the cylinder. The evolution of additional components of vorticity with features the same as mode A shows that (pure) mode A can be already formed in the late computational transition. Through careful analysis of the vorticity field on the front surface, in the shear layers and near wake at typical times, two sign laws are obtained. They illustrate intrinsic relationships among three vorticity components, irrelevant to the wavelength or Fourier mode and Reynolds number in (pure) mode A. Most importantly, the origin of streamwise vortices is found and explained by a new physical mechanism based on the theory of vortex-induced vortex. As a result, the whole process of formation and shedding vortices with these vorticities is firstly and completely illustrated. Other characteristics are presented in detail.
KeywordWake transition Circular cylinder Vorticity Mode A Sign law
Indexed BySCI ; EI ; CSCD
WOS IDWOS:000499122300001
WOS Research AreaEngineering, Mechanical ; Mechanics
WOS SubjectEngineering ; Mechanics
ContributorTan, ZR
Citation statistics
Cited Times:2[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Affiliation1.[Lin, L. M.] Chinese Acad Sci, Inst Mech, Key Lab Mech Fluid Solid Coupling Syst, Beijing 100190, Peoples R China
2.[Tan, Z. R.] Wuhan Univ Technol, Sch Nav, Wuhan 430063, Hubei, Peoples R China
3.[Tan, Z. R.] Wuhan Univ Technol, Hubei Key Lab Inland Shipping Technol, Wuhan 430063, Hubei, Peoples R China
Recommended Citation
GB/T 7714
Lin LM,Tan ZR. DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder: (pure) mode A[J]. ACTA MECHANICA SINICA,2019,35(6):1131-1149.
APA 林黎明,&Tan ZR.(2019).DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder: (pure) mode A.ACTA MECHANICA SINICA,35(6),1131-1149.
MLA 林黎明,et al."DNS in evolution of vorticity and sign relationship in wake transition of a circular cylinder: (pure) mode A".ACTA MECHANICA SINICA 35.6(2019):1131-1149.
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