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Title:Reynolds-stress enhancement associated with a short fetch of roughness in wall turbulence
Author(s):Yanhua Wu; Christensen, Kenneth T.; Kim, Tae-Yeon; Dolbow, John; Fried, Eliot
Subject(s):Reynolds Stress
Wall Turbulence
Short Fetch Of Roughness
Stress Producing Events
Abstract:Particle-image velocimetry experiments are performed to study the response of smoothwall turbulent channel flow to a short fetch of roughness (ten outer length scales long). The roughness studied herein is replicated from a surface scan of a damaged turbine blade and contains both large- and small-scale surface defects attributable to pitting, deposition and spallation. Quadrant analysis is used to investigate the characteristics of Reynolds stress- producing events within the internal layer that develops over the roughness. The total mean Reynolds stress is dramatically increased in the presence of the roughness as compared to the smooth-wall baseline owing to an increased number of extremely intense ejections and sweeps. In contrast, inward and outward interactions, as well as relatively weak ejection and sweep events, are found to be insensitive to the surface conditions. While the stress and space fractions for all Reynolds-stress-producing events are found to be insensitive to the s urface topology, the most intense ejection and sweep events yield stress and space fractions that vary significantly with the local surface topology.
Issue Date:2006-01
Publisher:Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report:TAM R 1085
Genre:Technical Report
Rights Information:Copyright 2006 Board of Trustees of the University of Illinois
Date Available in IDEALS:2021-11-04

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  • Technical Reports - Theoretical and Applied Mechanics (TAM)
    TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.

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