Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows

Andrea Zampiron; Vladimir Nikora; Stuart Cameron; Wada Patella; Isacco Valentini; Mark Stewart

doi:10.1061/(ASCE)HY.1943-7900.0001647

Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows

Andrea Zampiron^* (Corresponding Author), Vladimir Nikora, Stuart Cameron, Wada Patella, Isacco Valentini, Mark Stewart

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

7 Citations (Scopus)

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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 1.6H and lower by up to 20% at spacings smaller than 0.7H (H 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.

Original language	English
Article number	06019018
Number of pages	8
Journal	Journal of Hydraulic Engineering
Volume	146
Issue number	1
Early online date	23 Oct 2019
DOIs	https://doi.org/10.1061/(ASCE)HY.1943-7900.0001647
Publication status	Published - Jan 2020

Keywords

SECONDARY FLOWS
TURBULENCE
SURFACES

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Zampiron_etal_JHR_Streamwise_Ridges_AAM
This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HY.1943-7900.0001647
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Cite this

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title = "Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows",

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 1.6H and lower by up to 20% at spacings smaller than 0.7H (H 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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author = "Andrea Zampiron and Vladimir Nikora and Stuart Cameron and Wada Patella and Isacco Valentini and Mark Stewart",

note = "Funding Information: Financial support was provided by the EPSRC/UK grant “Bed Friction in Rough-Bed Free-Surface Flows: A Theoretical Frame-work, Roughness Regimes, and Quantification” (Grant No. EP/ K041088/1). Discussions with I. Marusic (University of Melbourne) and B. Ganapathisubramani (University of Southampton) are greatly ",

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AU - Patella, Wada

AU - Valentini, Isacco

AU - Stewart, Mark

N1 - Funding Information: Financial support was provided by the EPSRC/UK grant “Bed Friction in Rough-Bed Free-Surface Flows: A Theoretical Frame-work, Roughness Regimes, and Quantification” (Grant No. EP/ K041088/1). Discussions with I. Marusic (University of Melbourne) and B. Ganapathisubramani (University of Southampton) are greatly

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N2 - 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 1.6H and lower by up to 20% at spacings smaller than 0.7H (H 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.

AB - 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 1.6H and lower by up to 20% at spacings smaller than 0.7H (H 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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Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows

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Effects of Streamwise Ridges on Hydraulic Resistance in Open-Channel Flows

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