Synergistic Effects in Turbulent Drag Reduction by Riblets and Polymer Additives

[+] Author and Article Information
H. Mizunuma, K. Ueda

Department of Mechanical Engineering, Tokyo Metropolitan University, 1-1, Minamiohsawa, Hachioji-shi, Tokyo, 192-0397 Japan

Y. Yokouchi

Komatsu Forklift, 110, Yokokura-shinden, oyama-shi, Tochigi prefecture, 323-8567 Japan

J. Fluids Eng 121(3), 533-540 (Sep 01, 1999) (8 pages) doi:10.1115/1.2823501 History: Received July 31, 1996; Revised April 21, 1999; Online December 04, 2007


Drag reduction was investigated for the combined system of polymer additives and a riblet pipe. The riblet grooves were V-shaped, the spacing of which was 1.3 mm and the height of which was 1.01 mm. For higher h+ , a triangular riblet system including other geometries increases the drag to levels similar to those of normal transient roughness. This drag increase was generally given as a function of h+ . The polymer additives were Aronfloc N-110 and Separan AP-30. The critical shear stress τ*, at which N-110 started the drag reduction, was approximately eight times higher than τ* for AP-30. In the combined system, the synergistic drag reduction for higher h+ was discussed under the assumption that the additives suppressed the drag increase resulting from riblets. Since the additives thicken a wall layer covering the region from a viscous sublayer to a buffer layer, the relative height of h to this wall layer thickness is lowered. In addition, the flow enhancement due to additives relatively suppresses the riblet-induced drag increase. The analysis based on velocity profiles indicated that these effects can produce synergistic drag reduction for higher h+ .

Copyright © 1999 by The American Society of Mechanical Engineers
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