Double-averaged momentum and energy balances in open-channel flows over streamwise ridges

Stuart Cameron; Andrea Zampiron; Vladimir Nikora

doi:10.3850/IAHR-39WC252171192022419

Double-averaged momentum and energy balances in open-channel flows over streamwise ridges

Stuart Cameron^* (Corresponding Author), Andrea Zampiron, Vladimir Nikora

^*Corresponding author for this work

Engineering

Research output: Chapter in Book/Report/Conference proceeding › Published conference contribution

Abstract

Flows over beds covered with streamwise ridges exhibit counter-rotating cells in the time-averaged velocity field with associated streamwise vorticity. These secondary current cells scale with the inter-ridge spacing, interact with large-scale turbulent structures, and contribute to momentum and energy transfer within the flow with implications for mixing, bed friction, and sediment transport. A better understanding of the mechanisms that control the formation of secondary currents, their size and their strength may lead to improvements in the modelling, design, and management of open channels. The double-averaging (averaging in time and in space) methodology provides a useful framework to study flows over ridge covered beds, as with careful selection of the spanwise size of the averaging domain to a multiple of the ridge spacing, the equations are greatly simplified and terms in the momentum and energy balance equations are neatly partitioned into turbulence and secondary current contributions. In this study, we explore the distributions of these terms and their dependence on the inter-ridge spacing for the case of smooth triangular shaped ridges overlying a hydraulically rough bed.

Original language	English
Title of host publication	Proceedings of the 39th IAHR World Congress
Subtitle of host publication	From Snow to Sea
Editors	Miguel Ortega-Sánchez
Publisher	IAHR
Chapter	3
Pages	1612-1615
Number of pages	4
ISBN (Print)	978-90-832612-1-8
DOIs	https://doi.org/10.3850/IAHR-39WC252171192022419
Publication status	Published - 19 Jun 2022
Event	39th IAHR World Congress, 2022 - Granada, Spain Duration: 19 Jun 2022 → 24 Jun 2022

Publication series

Name	Proceedings of the IAHR World Congress
Publisher	IAHR
ISSN (Print)	2521-7119
ISSN (Electronic)	2521-716X

Conference

Conference	39th IAHR World Congress, 2022
Country/Territory	Spain
City	Granada
Period	19/06/22 → 24/06/22

Bibliographical note

Funding Information:
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 EP/K041088/1].

Keywords

Double-averaging methodology
Energy budget
Momentum balance
Open-channel flows
Secondary currents

Access to Document

10.3850/IAHR-39WC252171192022419Licence: Unspecified

Cite this

Double-averaged momentum and energy balances in open-channel flows over streamwise ridges. / Cameron, Stuart (Corresponding Author); Zampiron, Andrea; Nikora, Vladimir.
Proceedings of the 39th IAHR World Congress: From Snow to Sea. ed. / Miguel Ortega-Sánchez. IAHR, 2022. p. 1612-1615 (Proceedings of the IAHR World Congress).

Research output: Chapter in Book/Report/Conference proceeding › Published conference contribution

Cameron, S, Zampiron, A & Nikora, V 2022, Double-averaged momentum and energy balances in open-channel flows over streamwise ridges. in M Ortega-Sánchez (ed.), Proceedings of the 39th IAHR World Congress: From Snow to Sea. Proceedings of the IAHR World Congress, IAHR, pp. 1612-1615, 39th IAHR World Congress, 2022, Granada, Spain, 19/06/22. https://doi.org/10.3850/IAHR-39WC252171192022419

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N2 - Flows over beds covered with streamwise ridges exhibit counter-rotating cells in the time-averaged velocity field with associated streamwise vorticity. These secondary current cells scale with the inter-ridge spacing, interact with large-scale turbulent structures, and contribute to momentum and energy transfer within the flow with implications for mixing, bed friction, and sediment transport. A better understanding of the mechanisms that control the formation of secondary currents, their size and their strength may lead to improvements in the modelling, design, and management of open channels. The double-averaging (averaging in time and in space) methodology provides a useful framework to study flows over ridge covered beds, as with careful selection of the spanwise size of the averaging domain to a multiple of the ridge spacing, the equations are greatly simplified and terms in the momentum and energy balance equations are neatly partitioned into turbulence and secondary current contributions. In this study, we explore the distributions of these terms and their dependence on the inter-ridge spacing for the case of smooth triangular shaped ridges overlying a hydraulically rough bed.

AB - Flows over beds covered with streamwise ridges exhibit counter-rotating cells in the time-averaged velocity field with associated streamwise vorticity. These secondary current cells scale with the inter-ridge spacing, interact with large-scale turbulent structures, and contribute to momentum and energy transfer within the flow with implications for mixing, bed friction, and sediment transport. A better understanding of the mechanisms that control the formation of secondary currents, their size and their strength may lead to improvements in the modelling, design, and management of open channels. The double-averaging (averaging in time and in space) methodology provides a useful framework to study flows over ridge covered beds, as with careful selection of the spanwise size of the averaging domain to a multiple of the ridge spacing, the equations are greatly simplified and terms in the momentum and energy balance equations are neatly partitioned into turbulence and secondary current contributions. In this study, we explore the distributions of these terms and their dependence on the inter-ridge spacing for the case of smooth triangular shaped ridges overlying a hydraulically rough bed.

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Double-averaged momentum and energy balances in open-channel flows over streamwise ridges

Abstract

Publication series

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Bibliographical note

Keywords

Access to Document

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