Coherent structures in a screen cylinder wake

Azlin Mohd Azmi, Tongming Zhou, Yu Zhou, Hanfeng Wang, and Liang Cheng
Phys. Rev. Fluids 3, 074702 – Published 13 July 2018

Abstract

Experiments were conducted in a wind tunnel to examine the development of coherent structures in a screen cylinder wake over a streamwise range of 10x/d60 (where d is the diameter of the cylinder) at a Reynolds number Re of 7000. The screen cylinder was made of a stainless-steel wire mesh with a porosity (open area ratio) of 67%. Results showed that the flow can be classified into two distinct regimes, characterized by the averaged contributions from the coherent motion to the Reynolds stresses where vortices changed from growing to decaying. The first regime exhibited the growth of small-scale Kelvin-Helmholtz vortices in the shear layer through vortex merging. These small-scale vortices matured quite a distance downstream to form the “large-scale” coherent structures, marked by the change of the root-mean-square transverse velocity fluctuations from a twin-peak to a single peak profile, significantly extending the vortex formation length. The second regime was manifested by the slow decay of the fully formed large-scale vortices, designated by the weak vorticity exchange across the wake centerline. Conceptual models of the vortex formation and decay processes as well as the momentum transport in the screen cylinder wake were proposed and illustrated, and comparisons were made with that of a solid cylinder wake.

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  • Received 23 March 2018

DOI:https://doi.org/10.1103/PhysRevFluids.3.074702

©2018 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Azlin Mohd Azmi1, Tongming Zhou2,*, Yu Zhou3, Hanfeng Wang4, and Liang Cheng2

  • 1Faculty of Mechanical Engineering, Universiti Teknologi MARA, 40450 Shah Alam, Selangor, Malaysia
  • 2Department of Civil, Environmental and Mining Engineering, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
  • 3Institute for Turbulence-Noise-Vibration Interaction and Control, Shen Zhen Graduate School, Harbin Institute of Technology, People's Republic of China
  • 4School of Civil Engineering and Architecture, Central South University, Changsha, People's Republic of China

  • *Author to whom all correspondence should be addressed: tongming.zhou@uwa.edu.au

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Vol. 3, Iss. 7 — July 2018

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