Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows
Publication: Journal of Hydraulic Engineering
Volume 146, Issue 1
Abstract
This Technical Note reports on new experiments focused on hydraulic resistance in open-channel flows over beds covered with streamwise ridges. Extensive bulk friction factor measurements, combined with particle image velocimetry (PIV) for selected cases, were carried out to investigate the effects of spanwise spacing, relative submergence, and surface roughness of the ridges. Two types of ridges were investigated, both characterized by triangular cross sections but featuring different surface roughness. Compared to friction factor estimates neglecting any changes in flow structure promoted by the ridges, the measured friction factors were found to be higher by 10% at ridge spacings of approximately and lower by up to 20% at spacings smaller than ( is flow depth). No influence of relative submergence and ridge surface roughness on these findings was observed. The PIV data suggest that the revealed effects are likely related to secondary currents instigated and modulated by the bed ridges.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the submitted article.
Acknowledgments
Financial support was provided by the EPSRC/UK grant “Bed Friction in Rough-Bed Free-Surface Flows: A Theoretical Framework, Roughness Regimes, and Quantification” (Grant No. EP/K041088/1). Discussions with I. Marusic (University of Melbourne) and B. Ganapathisubramani (University of Southampton) are greatly appreciated. The comments of the editor, associate editor, and four reviewers helped significantly to improve the Note to the final version.
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Published In
Journal of Hydraulic Engineering
Volume 146 • Issue 1 • January 2020
Copyright
©2019 American Society of Civil Engineers.
History
Received: Jun 16, 2018
Accepted: Apr 16, 2019
Published online: Oct 23, 2019
Published in print: Jan 1, 2020
Discussion open until: Mar 23, 2020
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