Affordable Access

Publisher Website

Spanwise phase transition between pure modes A and B in a circular cylinder’s wake. Part II: spatiotemporal evolution of vorticity

Authors
  • Lin, L M
Type
Published Article
Journal
Fluid Dynamics Research
Publisher
IOP Publishing
Publication Date
Oct 01, 2023
Volume
55
Issue
5
Identifiers
DOI: 10.1088/1873-7005/ad02ba
Source
ioppublishing
Keywords
Disciplines
  • Paper
License
Unknown

Abstract

Through direct numerical simulation, the transition from pure mode A to mode B in the near wake of a circular cylinder is studied without consideration of vortex dislocations. The Reynolds number Re is calculated from 100 to 330 with a computational spanwise length of 4 diameters. In the present section, the spatiotemporal evolution of the vorticity and its sign are analyzed. The results show that mode B, as a kind of weak disturbed vorticity with opposite signs, actually appears partially on the rear surface of the cylinder and in the shear layers once Re exceeds 193. With increasing Re , the vortex-shedding patterns in the near wake undergo the initial generation stage of mode B coupling with the fully developed pure mode A ( 193⩽Re<230 ), the mode swapping or coexistence stage between modes A and B ( 230⩽Re<260∼265 ), the self-adjustment stage of the nondimensional spanwise wavelength from 0.8 to 1 in dominant mode B ( 260∼265⩽Re<310 ), and the full development stage of mode B ( Re⩾310 ). In particular, the spanwise phase transition initially occurs at a certain spanwise position in the initial generation stage where a part of mode A and a part of mode B with specific vorticity signs appear, e.g. the Π− vortex in mode A and the Π+ vortex in mode B, in which Π− and Π+ vortices are vortices with three vorticity components satisfying the vorticity sign law and shed from the upper and lower shear layers, respectively.

Report this publication

Statistics

Seen <100 times