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PIV measurements of near wake behind a U-grooved cylinder SCIE SCOPUS

Title
PIV measurements of near wake behind a U-grooved cylinder
Authors
Lim, HCLee, SJ
Date Issued
2003-08
Publisher
ACADEMIC PRESS LTD ELSEVIER SCIENCE L
Abstract
The flow structure around a circular cylinder with U-grooved surfaces has been investigated experimentally. The results were compared with that of a smooth cylinder having the same diameter. Drag force and turbulence statistics of wake behind each cylinder were measured for Reynolds numbers based on the cylinder diameter (D = 60 mm) in the range Re-D = 8 X 10(3) - 1.4 x 10(5). At Re-D = 1.4 x 10(5), the U-type grooves reduce the drag coefficient acting on the cylinder by 18.6%, compared with that of smooth cylinder. The flow characteristics of wake behind the U-grooved cylinder have been analyzed using two kinds of particle image velocimetry (PIV) velocity measurement techniques, cinematic PIV and high-resolution PIV. Consecutive instantaneous velocity fields were measured using the cinematic PIV technique at time interval of 5 ms, corresponding to about 1% of the vortex shedding frequency of the wake. The instantaneous velocity fields measured with the high-resolution PIV technique were ensemble-averaged to get the spatial distributions of turbulent statistics including turbulent intensities and turbulent kinetic energy. For the case of smooth cylinder, large-scale vortices formed behind the cylinder maintain round shape and do not spread out noticeably in the near wake. However, for the case of U-grooved cylinder, the vortices are largely distorted and spread out significantly as they go downstream. The longitudinal grooves seem to shift the location of spanwise vortices toward the cylinder, reducing the vortex formation region, compared with the smooth cylinder. The sharp peaks of longitudinal U-shaped grooves also suppress the formation of large-scale secondary streamwise vortices. The secondary vortices are broken into smaller eddies, reducing turbulent kinetic energy in the near-wake region. (C) 2003 Elsevier Ltd. All rights reserved.
Keywords
CIRCULAR-CYLINDERS; SURFACE-ROUGHNESS; MEAN FLOW; RIBLETS
URI
https://oasis.postech.ac.kr/handle/2014.oak/18308
DOI
10.1016/S0889-9746(03)00086-0
ISSN
0889-9746
Article Type
Article
Citation
JOURNAL OF FLUIDS AND STRUCTURES, vol. 18, no. 1, page. 119 - 130, 2003-08
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이상준LEE, SANG JOON
Dept of Mechanical Enginrg
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