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Drag reduction in a rectangular duct usingriblets

Published online by Cambridge University Press:  04 July 2016

A. R. Moore
Affiliation:
Department of Aerospace EngineeringUniversity of Bristol, Bristol, UK
M. V. Lowson
Affiliation:
Department of Aerospace EngineeringUniversity of Bristol, Bristol, UK

Abstract

An experimental investigation has been made into theeffects of riblets on the drag in a rectangular ductof aspect ratio 10. It has been found that a maximumdrag reduction of approximately 10% occurs in fullydeveloped turbulent flow. This figure is larger thanthe 6–8% drag reduction usually found for externalflow. The maximum drag reduction occurred when theheight of the riblets was between 7 and 13 wallunits. Analysis of the developing region of the flowhas shown a maximum drag reduction of approximately8% at a wall unit value of 13, consistent withresults in external flows. The effects of riblets ontransition has also been investigated. It was foundthat riblets delayed transition by 2–4% in criticalRe as measured by peak flatness, and caused someextension in the length of the transition process,so that the completion of transition was delayed bybetween 4–8%, with the stronger effect at the lowerReynolds numbers.

Information

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society 1995 

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