Turbulent length scales and budgets of Reynolds stress-transport for open-channel flows; friction Reynolds numbers (R-e tau)=150, 400 and 1020

Umair Ahmed; David Apsley; Timothy Stallard; Peter Stansby; Imran Afgan

doi:10.1080/00221686.2020.1729265

Turbulent length scales and budgets of Reynolds stress-transport for open-channel flows; friction Reynolds numbers (R-e tau)=150, 400 and 1020

Umair Ahmed, David Apsley, Timothy Stallard, Peter Stansby, Imran Afgan

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Abstract

Turbulence in open channel flows is ubiquitous to hydro-environmental applications and has recently increased in importance with the deployment
of tidal stream turbines, as turbulence impacts both the turbine performance and the blade fatigue life. Tidal turbine analysis requires fully developed
turbulence characteristics at the inlet of numerical simulations where generally the length scale information is limited. In this study, fully resolved
large eddy simulations (LES) with flat beds were undertaken using an open source code at friction Reynolds numbers (Reτ) of 150, 400 and 1020. It
was found that the effects of the free surface on turbulence length scales were felt in approximately the uppermost 10% of the channel only, although
the influence on Reynolds stresses extended further downwards. Furthermore, the cross-correlation length scales of both streamwise and spanwise
velocities were found to be significantly affected by the free surface where turbulent eddies were flattened to the two-component limit.

Original language	English
Pages (from-to)	1-15
Journal	Journal of Hydraulic Research
Early online date	27 Mar 2020
DOIs	https://doi.org/10.1080/00221686.2020.1729265
Publication status	Published - 3 Apr 2020

Keywords

Anisotropy
budgets
open-channel flow
tidal stream turbines
turbulence length scales
turbulence spectra

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1080/00221686.2020.1729265

Turbulent length scales and budgets of Reynolds stress transport for open channel flows friction Reynolds numbers Re 150 400 and 1020Final published version, 3.68 MB

https://www.tandfonline.com/doi/full/10.1080/00221686.2020.1729265

1 Finished
1 Active

Offshore Engineering and Energy
Stallard, T. (PI), Stansby, P. (PI), Draycott, S. (PI), Ouro, P. (PI), Mullings, H. (PI), Tang, T. (PI), Ali, K. (PGR student), Liao, Z. (Researcher), Mohamed, O. S. (Researcher), Araya Araya, D. (Researcher) & Zhang, Y. (Researcher)
1/01/05 → …
Project: Research
X-MED : Extreme Loading of Marine Energy Devices due to Waves, Current, Flotsam and Mammal Impact.
Stansby, P. (PI), Apsley, D. (CoI), Revell, A. (CoI), Rogers, B. D. (CoI) & Stallard, T. (CoI)
1/02/12 → 31/01/15
Project: Research

Cite this

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title = "Turbulent length scales and budgets of Reynolds stress-transport for open-channel flows; friction Reynolds numbers (R-e tau)=150, 400 and 1020",

abstract = "Turbulence in open channel flows is ubiquitous to hydro-environmental applications and has recently increased in importance with the deployment of tidal stream turbines, as turbulence impacts both the turbine performance and the blade fatigue life. Tidal turbine analysis requires fully developed turbulence characteristics at the inlet of numerical simulations where generally the length scale information is limited. In this study, fully resolved large eddy simulations (LES) with flat beds were undertaken using an open source code at friction Reynolds numbers (Reτ) of 150, 400 and 1020. It was found that the effects of the free surface on turbulence length scales were felt in approximately the uppermost 10\% of the channel only, although the influence on Reynolds stresses extended further downwards. Furthermore, the cross-correlation length scales of both streamwise and spanwise velocities were found to be significantly affected by the free surface where turbulent eddies were flattened to the two-component limit.",

keywords = "Anisotropy, budgets, open-channel flow, tidal stream turbines, turbulence length scales, turbulence spectra",

author = "Umair Ahmed and David Apsley and Timothy Stallard and Peter Stansby and Imran Afgan",

note = "Publisher Copyright: {\textcopyright} 2020, {\textcopyright} 2020 International Association for Hydro-Environment Engineering and Research. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.",

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doi = "10.1080/00221686.2020.1729265",

language = "English",

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T1 - Turbulent length scales and budgets of Reynolds stress-transport for open-channel flows; friction Reynolds numbers (R-e tau)=150, 400 and 1020

AU - Ahmed, Umair

AU - Apsley, David

AU - Stallard, Timothy

AU - Stansby, Peter

AU - Afgan, Imran

PY - 2020/4/3

Y1 - 2020/4/3

N2 - Turbulence in open channel flows is ubiquitous to hydro-environmental applications and has recently increased in importance with the deployment of tidal stream turbines, as turbulence impacts both the turbine performance and the blade fatigue life. Tidal turbine analysis requires fully developed turbulence characteristics at the inlet of numerical simulations where generally the length scale information is limited. In this study, fully resolved large eddy simulations (LES) with flat beds were undertaken using an open source code at friction Reynolds numbers (Reτ) of 150, 400 and 1020. It was found that the effects of the free surface on turbulence length scales were felt in approximately the uppermost 10% of the channel only, although the influence on Reynolds stresses extended further downwards. Furthermore, the cross-correlation length scales of both streamwise and spanwise velocities were found to be significantly affected by the free surface where turbulent eddies were flattened to the two-component limit.

AB - Turbulence in open channel flows is ubiquitous to hydro-environmental applications and has recently increased in importance with the deployment of tidal stream turbines, as turbulence impacts both the turbine performance and the blade fatigue life. Tidal turbine analysis requires fully developed turbulence characteristics at the inlet of numerical simulations where generally the length scale information is limited. In this study, fully resolved large eddy simulations (LES) with flat beds were undertaken using an open source code at friction Reynolds numbers (Reτ) of 150, 400 and 1020. It was found that the effects of the free surface on turbulence length scales were felt in approximately the uppermost 10% of the channel only, although the influence on Reynolds stresses extended further downwards. Furthermore, the cross-correlation length scales of both streamwise and spanwise velocities were found to be significantly affected by the free surface where turbulent eddies were flattened to the two-component limit.

KW - Anisotropy

KW - budgets

KW - open-channel flow

KW - tidal stream turbines

KW - turbulence length scales

KW - turbulence spectra

U2 - 10.1080/00221686.2020.1729265

DO - 10.1080/00221686.2020.1729265

M3 - Article

SN - 0022-1686

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JO - Journal of Hydraulic Research

JF - Journal of Hydraulic Research

ER -

Turbulent length scales and budgets of Reynolds stress-transport for open-channel flows; friction Reynolds numbers (R-e tau)=150, 400 and 1020

Abstract

Keywords

UN SDGs

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Projects

Offshore Engineering and Energy

X-MED : Extreme Loading of Marine Energy Devices due to Waves, Current, Flotsam and Mammal Impact.

Cite this