Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies

Otto Neshamar; Niels G. Jacobsen; Dominic Van der A; Thomas O'Donoghue

doi:10.1080/00221686.2023.2231433

Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies

Otto Neshamar^* (Corresponding Author), Niels G. Jacobsen, Dominic Van der A, Thomas O'Donoghue

^*Corresponding author for this work

Engineering

Deltares

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Abstract

An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2–0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearisation of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocityskewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity.

Original language	English
Pages (from-to)	668-685
Number of pages	18
Journal	Journal of Hydraulic Research
Volume	61
Issue number	5
Early online date	15 Sept 2023
DOIs	https://doi.org/10.1080/00221686.2023.2231433
Publication status	Published - 15 Sept 2023

Bibliographical note

Acknowledgement
ON acknowledges funding from the University of Aberdeen to support his PhD. The authors ac knowledge the support of the University of Aberdeen technical staff for the experimental work, especially that of Fluids Laboratory Technician Roy Gillanders. The experimental dataset is avail626 able on https://dx.doi.org/10.5281/zenodo.4560141 (will be released upon acceptance of the manuscript).

Keywords

oscillatory flow
drag force
canopies
velocity reduction
nonlinear momentum transfer

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10.1080/00221686.2023.2231433Licence: CC BY

Neshamar_etal_JHR_Linear_And_Nonlinear_VoR
© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.
Final published version, 4.55 MBLicence: CC BY

Cite this

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title = "Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies",

abstract = "An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2–0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearisation of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocityskewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity.",

keywords = "oscillatory flow, drag force, canopies, velocity reduction, nonlinear momentum transfer",

author = "Otto Neshamar and Jacobsen, {Niels G.} and {Van der A}, Dominic and Thomas O'Donoghue",

note = "Acknowledgement ON acknowledges funding from the University of Aberdeen to support his PhD. The authors ac knowledge the support of the University of Aberdeen technical staff for the experimental work, especially that of Fluids Laboratory Technician Roy Gillanders. The experimental dataset is avail626 able on https://dx.doi.org/10.5281/zenodo.4560141 (will be released upon acceptance of the manuscript). ",

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T1 - Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies

AU - Neshamar, Otto

AU - Jacobsen, Niels G.

AU - Van der A, Dominic

AU - O'Donoghue, Thomas

N1 - Acknowledgement ON acknowledges funding from the University of Aberdeen to support his PhD. The authors ac knowledge the support of the University of Aberdeen technical staff for the experimental work, especially that of Fluids Laboratory Technician Roy Gillanders. The experimental dataset is avail626 able on https://dx.doi.org/10.5281/zenodo.4560141 (will be released upon acceptance of the manuscript).

PY - 2023/9/15

Y1 - 2023/9/15

N2 - An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2–0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearisation of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocityskewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity.

AB - An analytical and experimental study of flow velocities within submerged canopies of rigid cylinders under oscillatory flows is presented, providing insights into the momentum transfer mechanisms between the different flow harmonics. The experimental dataset covers an unprecedented wide range of flow amplitudes with in-canopy velocity reductions ranging between 0.2–0.8 of the free stream velocity (from inertia- to drag-dominated in-canopy flow). Results from the analytical model with nonlinear drag compare favourably to the experimental data. Having application of theories for free surface waves over canopies in mind, the effects of linearisation of the drag are analysed by comparing sinusoidal and nonlinear model predictions. Finally, a unified prediction formula for in-canopy velocities for sinusoidal, velocityskewed, and velocity-asymmetric free stream velocities is presented. The formula depends on two non-dimensional parameters related to inertia and drag forces, and the unified formula allows for easy assessment of the maximum in-canopy velocity.

KW - oscillatory flow

KW - drag force

KW - canopies

KW - velocity reduction

KW - nonlinear momentum transfer

U2 - 10.1080/00221686.2023.2231433

DO - 10.1080/00221686.2023.2231433

M3 - Article

SN - 0022-1686

VL - 61

SP - 668

EP - 685

JO - Journal of Hydraulic Research

JF - Journal of Hydraulic Research

IS - 5

ER -

Linear and nonlinear frequency-domain modelling of oscillatory flow over submerged canopies

Abstract

Bibliographical note

Keywords

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