Meandering of instantaneous large-scale structures in open-channel flow over longitudinal ridges

Qianyu Luo; Thorsten Stoesser; Stuart Cameron; Vladimir Nikora; Andrea Zampiron; Wada Patella

doi:10.1007/s10652-023-09934-0

Meandering of instantaneous large-scale structures in open-channel flow over longitudinal ridges

Qianyu Luo, Thorsten Stoesser^*, Stuart Cameron, Vladimir Nikora, Andrea Zampiron, Wada Patella

^*Corresponding author for this work

University College London

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

1 Citation (Scopus)

Abstract

The results of large-eddy simulations of open-channel flows over spanwise heterogeneous surface ridges at two representative spanwise spacings are presented. Flows at moderate Froude and Reynolds numbers over smooth channel beds with streamwise-orientated rectangular ridges are considered. The ridge spacing has a profound effect on the flow: at small spacing relatively small secondary cells occur, whilst at large ridge spacing secondary cells occupy the entire flow depth. The instantaneous flow features secondary flow instabilities and the meandering of alternating low- and high-momentum regions. The quasi-periodical nature of the meandering of the instantaneous large-scale motion is visualised and quantified for both ridge spacings. Although time-averaged clockwise and counter-clockwise secondary current cells are symmetrical about the ridge-axis, they exhibit quasi-periodical increase and decrease in size as well as lateral and vertical movement in space over the meandering period.

Original language	English
Journal	Environmental Fluid Mechanics
Early online date	1 Aug 2023
DOIs	https://doi.org/10.1007/s10652-023-09934-0
Publication status	E-pub ahead of print - 1 Aug 2023

Bibliographical note

Funding Information:
The work presented in this paper is supported by the EPSRC under Project Numbers EP/R022135/1, EP/V002384/1 and EP/V002414/1. The simulations were carried out on UCL’s supercomputer Kathleen. The first author is funded by UCL’s Department of Civil, Environmental and Geomatic Engineering. The authors are thankful to the reviewers for their useful comments.

Publisher Copyright:
© 2023, The Author(s).

Keywords

Meandering
Open channel flow
Secondary currents
Spanwise heterogeneity

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Cite this

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title = "Meandering of instantaneous large-scale structures in open-channel flow over longitudinal ridges",

abstract = "The results of large-eddy simulations of open-channel flows over spanwise heterogeneous surface ridges at two representative spanwise spacings are presented. Flows at moderate Froude and Reynolds numbers over smooth channel beds with streamwise-orientated rectangular ridges are considered. The ridge spacing has a profound effect on the flow: at small spacing relatively small secondary cells occur, whilst at large ridge spacing secondary cells occupy the entire flow depth. The instantaneous flow features secondary flow instabilities and the meandering of alternating low- and high-momentum regions. The quasi-periodical nature of the meandering of the instantaneous large-scale motion is visualised and quantified for both ridge spacings. Although time-averaged clockwise and counter-clockwise secondary current cells are symmetrical about the ridge-axis, they exhibit quasi-periodical increase and decrease in size as well as lateral and vertical movement in space over the meandering period.",

keywords = "Meandering, Open channel flow, Secondary currents, Spanwise heterogeneity",

author = "Qianyu Luo and Thorsten Stoesser and Stuart Cameron and Vladimir Nikora and Andrea Zampiron and Wada Patella",

note = "Funding Information: The work presented in this paper is supported by the EPSRC under Project Numbers EP/R022135/1, EP/V002384/1 and EP/V002414/1. The simulations were carried out on UCL{\textquoteright}s supercomputer Kathleen. The first author is funded by UCL{\textquoteright}s Department of Civil, Environmental and Geomatic Engineering. The authors are thankful to the reviewers for their useful comments. Publisher Copyright: {\textcopyright} 2023, The Author(s).",

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AU - Nikora, Vladimir

AU - Zampiron, Andrea

AU - Patella, Wada

N1 - Funding Information: The work presented in this paper is supported by the EPSRC under Project Numbers EP/R022135/1, EP/V002384/1 and EP/V002414/1. The simulations were carried out on UCL’s supercomputer Kathleen. The first author is funded by UCL’s Department of Civil, Environmental and Geomatic Engineering. The authors are thankful to the reviewers for their useful comments. Publisher Copyright: © 2023, The Author(s).

PY - 2023/8/1

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N2 - The results of large-eddy simulations of open-channel flows over spanwise heterogeneous surface ridges at two representative spanwise spacings are presented. Flows at moderate Froude and Reynolds numbers over smooth channel beds with streamwise-orientated rectangular ridges are considered. The ridge spacing has a profound effect on the flow: at small spacing relatively small secondary cells occur, whilst at large ridge spacing secondary cells occupy the entire flow depth. The instantaneous flow features secondary flow instabilities and the meandering of alternating low- and high-momentum regions. The quasi-periodical nature of the meandering of the instantaneous large-scale motion is visualised and quantified for both ridge spacings. Although time-averaged clockwise and counter-clockwise secondary current cells are symmetrical about the ridge-axis, they exhibit quasi-periodical increase and decrease in size as well as lateral and vertical movement in space over the meandering period.

AB - The results of large-eddy simulations of open-channel flows over spanwise heterogeneous surface ridges at two representative spanwise spacings are presented. Flows at moderate Froude and Reynolds numbers over smooth channel beds with streamwise-orientated rectangular ridges are considered. The ridge spacing has a profound effect on the flow: at small spacing relatively small secondary cells occur, whilst at large ridge spacing secondary cells occupy the entire flow depth. The instantaneous flow features secondary flow instabilities and the meandering of alternating low- and high-momentum regions. The quasi-periodical nature of the meandering of the instantaneous large-scale motion is visualised and quantified for both ridge spacings. Although time-averaged clockwise and counter-clockwise secondary current cells are symmetrical about the ridge-axis, they exhibit quasi-periodical increase and decrease in size as well as lateral and vertical movement in space over the meandering period.

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KW - Secondary currents

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JO - Environmental Fluid Mechanics

JF - Environmental Fluid Mechanics

ER -

Meandering of instantaneous large-scale structures in open-channel flow over longitudinal ridges

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Keywords

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