Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness

S. M. Cameron; V. I. Nikora; M. T. Stewart

doi:10.1201/b22619

Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness

S. M. Cameron, V. I. Nikora, M. T. Stewart

Engineering

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

Abstract

We explore the double-averaged momentum and energy conservation budgets for open-channel flows with hydraulically-rough beds. Three ‘self-affine’ roughness patterns were constructed with the spectra of surface height profiles designed to have power law scaling with exponents of -1, -5/3, and -3. Measurements were made using a ‘robotic’ stereoscopic PIV system that was programmed to record velocity fields in a sequence of planes on a periodic roughness tile. Our results showed that both secondary currents and roughness-induced near-bed spatial fluctuations of the time-averaged velocity contributed significantly to the dispersive stress. The distribution of drag force within the roughness canopy was shifted downwards for the ‘-3´ surface compared to the ‘-1´ surface reflecting increased penetration of the flow into the more open roughness structure. Production of turbulent energy via exchange with the double mean kinetic energy was found to be around three times larger than via exchange with the dispersive kinetic energy.

Original language	English
Title of host publication	River Flow 2020
Subtitle of host publication	Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020)
Editors	Wim Uijttewaal, Mario J. Franca, Daniel Valero, Victor Chavarrias, Claudia Ylla Arbos, Ralph Schielen, Ralph Schielen, Alessandra Crosato
Publisher	CRC Press/Balkema
Pages	31-37
Number of pages	7
ISBN (Electronic)	9780367627737
DOIs	https://doi.org/10.1201/b22619
Publication status	Published - 28 Aug 2020
Event	10th Conference on Fluvial Hydraulics, River Flow 2020 - Virtual, Online, Netherlands Duration: 7 Jul 2020 → 10 Jul 2020

Conference

Conference	10th Conference on Fluvial Hydraulics, River Flow 2020
Country/Territory	Netherlands
City	Virtual, Online
Period	7/07/20 → 10/07/20

Bibliographical note

Funding Information:
Financial support was provided by the EPSRC/UK project ‘Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification’ (grant EP/ K041088/1).

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https://www.taylorfrancis.com/chapters/edit/10.1201/b22619-8/double-averaged-momentum-energy-budgets-open-channel-flows-self-affine-bed-roughness-cameron-nikora-stewartLicence: Unspecified

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Cameron, S. M., Nikora, V. I., & Stewart, M. T. (2020). Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness. In W. Uijttewaal, M. J. Franca, D. Valero, V. Chavarrias, C. Y. Arbos, R. Schielen, R. Schielen, & A. Crosato (Eds.), River Flow 2020 : Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020) (pp. 31-37). CRC Press/Balkema. https://doi.org/10.1201/b22619

Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness. / Cameron, S. M.; Nikora, V. I.; Stewart, M. T.
River Flow 2020 : Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020). ed. / Wim Uijttewaal; Mario J. Franca; Daniel Valero; Victor Chavarrias; Claudia Ylla Arbos; Ralph Schielen; Ralph Schielen; Alessandra Crosato. CRC Press/Balkema, 2020. p. 31-37.

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

Cameron, SM , Nikora, VI & Stewart, MT 2020, Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness. in W Uijttewaal, MJ Franca, D Valero, V Chavarrias, CY Arbos, R Schielen, R Schielen & A Crosato (eds), River Flow 2020 : Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020). CRC Press/Balkema, pp. 31-37, 10th Conference on Fluvial Hydraulics, River Flow 2020, Virtual, Online, Netherlands, 7/07/20. https://doi.org/10.1201/b22619

Cameron SM , Nikora VI , Stewart MT. Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness. In Uijttewaal W, Franca MJ, Valero D, Chavarrias V, Arbos CY, Schielen R, Schielen R, Crosato A, editors, River Flow 2020 : Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020). CRC Press/Balkema. 2020. p. 31-37 doi: 10.1201/b22619

Cameron, S. M. ; Nikora, V. I. ; Stewart, M. T. / Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness. River Flow 2020 : Proceedings of the 10th Conference on Fluvial Hydraulics (Delft, Netherlands, 7-10 July 2020). editor / Wim Uijttewaal ; Mario J. Franca ; Daniel Valero ; Victor Chavarrias ; Claudia Ylla Arbos ; Ralph Schielen ; Ralph Schielen ; Alessandra Crosato. CRC Press/Balkema, 2020. pp. 31-37

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abstract = "We explore the double-averaged momentum and energy conservation budgets for open-channel flows with hydraulically-rough beds. Three {\textquoteleft}self-affine{\textquoteright} roughness patterns were constructed with the spectra of surface height profiles designed to have power law scaling with exponents of -1, -5/3, and -3. Measurements were made using a {\textquoteleft}robotic{\textquoteright} stereoscopic PIV system that was programmed to record velocity fields in a sequence of planes on a periodic roughness tile. Our results showed that both secondary currents and roughness-induced near-bed spatial fluctuations of the time-averaged velocity contributed significantly to the dispersive stress. The distribution of drag force within the roughness canopy was shifted downwards for the {\textquoteleft}-3´ surface compared to the {\textquoteleft}-1´ surface reflecting increased penetration of the flow into the more open roughness structure. Production of turbulent energy via exchange with the double mean kinetic energy was found to be around three times larger than via exchange with the dispersive kinetic energy.",

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note = "Funding Information: Financial support was provided by the EPSRC/UK project {\textquoteleft}Bed friction in rough-bed free-surface flows: a theoretical framework, roughness regimes, and quantification{\textquoteright} (grant EP/ K041088/1). ; 10th Conference on Fluvial Hydraulics, River Flow 2020 ; Conference date: 07-07-2020 Through 10-07-2020",

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N2 - We explore the double-averaged momentum and energy conservation budgets for open-channel flows with hydraulically-rough beds. Three ‘self-affine’ roughness patterns were constructed with the spectra of surface height profiles designed to have power law scaling with exponents of -1, -5/3, and -3. Measurements were made using a ‘robotic’ stereoscopic PIV system that was programmed to record velocity fields in a sequence of planes on a periodic roughness tile. Our results showed that both secondary currents and roughness-induced near-bed spatial fluctuations of the time-averaged velocity contributed significantly to the dispersive stress. The distribution of drag force within the roughness canopy was shifted downwards for the ‘-3´ surface compared to the ‘-1´ surface reflecting increased penetration of the flow into the more open roughness structure. Production of turbulent energy via exchange with the double mean kinetic energy was found to be around three times larger than via exchange with the dispersive kinetic energy.

AB - We explore the double-averaged momentum and energy conservation budgets for open-channel flows with hydraulically-rough beds. Three ‘self-affine’ roughness patterns were constructed with the spectra of surface height profiles designed to have power law scaling with exponents of -1, -5/3, and -3. Measurements were made using a ‘robotic’ stereoscopic PIV system that was programmed to record velocity fields in a sequence of planes on a periodic roughness tile. Our results showed that both secondary currents and roughness-induced near-bed spatial fluctuations of the time-averaged velocity contributed significantly to the dispersive stress. The distribution of drag force within the roughness canopy was shifted downwards for the ‘-3´ surface compared to the ‘-1´ surface reflecting increased penetration of the flow into the more open roughness structure. Production of turbulent energy via exchange with the double mean kinetic energy was found to be around three times larger than via exchange with the dispersive kinetic energy.

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Double-averaged momentum and energy budgets for open-channel flows over self-affine bed roughness

Abstract

Conference

Bibliographical note

UN SDGs

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