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Advances in Mechanical Engineering
Volume 2011 (2011), Article ID 120438, 12 pages
http://dx.doi.org/10.1155/2011/120438
Research Article

Experimental Investigation on Zonal Structure in Drag-Reducing Channel Flow with Surfactant Additives

1Department of Mechanical Engineering, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510, Japan
2School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200230, China

Received 9 June 2011; Accepted 18 July 2011

Academic Editor: Jinjia Wei

Copyright © 2011 Masaaki Motozawa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The spatial structure of a drag-reducing channel flow with surfactant additives in a two-dimensional channel was investigated experimentally. We carried out detailed measurements of the instantaneous velocity in the streamwise wall-normal plane and streamwise spanwise plane by using particle image velocimetry (PIV). The surfactant used in this experiment is a kind of cationic surfactant CTAC. The weight concentrations of the CTAC solution were 25 and 40 ppm on the flow. We considered the effects of Reynolds number ranging from 10000 to 25000 and the weight concentration of CTAC. The results of this paper showed that in the drag-reducing flow, there appeared an area where the root mean square of streamwise velocity fluctuation and the vorticity fluctuation sharply decreased. This indicated that two layers with different turbulent structure coexisted on the boundary of this area. Moreover, these layers had characteristic flow structures, as confirmed by observation of the instantaneous vorticity fluctuation map.