University of Illinois Urbana-Champaign

Autogeneration of three-dimensional vortical structures in near wake of circular cylinder

Mittal, Rajat; Balachandar, S.

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https://hdl.handle.net/2142/112511

Description

Title
Autogeneration of three-dimensional vortical structures in near wake of circular cylinder
Author(s)
  • Mittal, Rajat
  • Balachandar, S.
Issue Date
1995-11
Keyword(s)
  • Three-dimensional Vortical Structures
  • Near Wake
  • Circular Cylinder
Abstract
A direct numerical simulation has been used to study the generation and evolution of streamwise vortices in the near wake of a circular cylinder at a Reynolds number of 300. In this study, the mechanism by which streamwise vortices are generated periodically in the near wake is studied without the complicating effect of a spanwise subharmonic mode. It is observed that streamwise vortices are generated due to the stretching induced by the span wise vortices. The spanwise vortices develop significant distortions along their axis due to the action of the stream wise vortices, but large scale entrainment of vorticity from the core of the spanwise vortices into the braid region is not observed indicating that the formation of the streamwise vortices can be accomplished without such entrainment. The span wise distortion of the span wise vortices does however play a crucial role in the autogeneration process since this results in a distortion of the stretching field which in turn has a direct influence on the growth rate and location of new streamwise vortices. The evolution of the spanwise vortices is also followed closely and this provides further insight into the interaction of the various vortical structures in near wake. The current study clearly indicates that the autogeneration process involves a feedback mechanism whereby the older generation streamwise vortices play a crucial role in the generation of new streamwise vortices. Thus, this mechanism cannot be characterized within the conventional framework of core or braid instability mechanisms alone which are primarily based on the temporal evolution of the flow.
Publisher
Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report Name or Number
  • TAM R 812
  • 1995-6034
ISSN
0073-5264
Type of Resource
text
Language
eng
Permalink
http://hdl.handle.net/2142/112511
Copyright and License Information
Copyright 1995 Board of Trustees of the University of Illinois

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