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Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis

Michael Togneri Orcid Logo, Ian Masters Orcid Logo, Iain Fairley

Ocean Engineering, Volume: 237, Start page: 109523

Swansea University Authors: Michael Togneri Orcid Logo, Ian Masters Orcid Logo, Iain Fairley

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DOI (Published version): 10.1016/j.oceaneng.2021.109523

Abstract

Acoustic Doppler current profilers (ADCPs) are the standard tool for measuring tidal currents at tidal stream energy sites; they are used to estimate several parameters, including turbulent kinetic energy (TKE). However, estimates of TKE from ADCPs are often swamped by wave action. We surmise that t...

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Published in: Ocean Engineering
ISSN: 0029-8018
Published: Elsevier BV 2021
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URI: https://cronfa.swan.ac.uk/Record/cronfa57524
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However, estimates of TKE from ADCPs are often swamped by wave action. We surmise that this bias can be detected as a data mode: to test this, we present an empirical orthogonal function (EOF) analysis of two months of TKE estimates from ADCP measurements at a tidal energy site with significant wave activity. The results of the analysis were compared with linear wave theory, using data from a wave buoy. The first data mode identified from EOF analysis agrees well with the wave bias predicted by linear theory, and the resulting decomposition of the data set into wave and turbulent components appears realistic. This decomposition is possible from ADCP data alone, and therefore offers a novel and widely applicable analysis technique for simultaneous assessment of turbulence and waves at highly-energetic tidal sites. The method can also be applied retrospectively to historical data sets. We also show that the decomposition can be improved by including higher EOF modes, but this requires an independent measurement of waves to determine the optimum number of modes.</abstract><type>Journal Article</type><journal>Ocean Engineering</journal><volume>237</volume><journalNumber/><paginationStart>109523</paginationStart><paginationEnd/><publisher>Elsevier BV</publisher><placeOfPublication/><isbnPrint/><isbnElectronic/><issnPrint>0029-8018</issnPrint><issnElectronic/><keywords>Waves, Turbulence, Turbulent kinetic energy, Empirical orthogonal analysis, Tidal power</keywords><publishedDay>1</publishedDay><publishedMonth>10</publishedMonth><publishedYear>2021</publishedYear><publishedDate>2021-10-01</publishedDate><doi>10.1016/j.oceaneng.2021.109523</doi><url/><notes/><college>COLLEGE NANME</college><department>Mechanical Engineering</department><CollegeCode>COLLEGE CODE</CollegeCode><DepartmentCode>MECH</DepartmentCode><institution>Swansea University</institution><apcterm/><funders>The authors acknowledge the support of the Welsh Assembly Government through the S&#xEA;r Cymru National Research network for Low Carbon, Energy and Environment, of EPSRC, United Kingdom through the projects SURFTEC (EP/P008628/1) and WTIMTS (funded via the Supergen ORE Hub, EP/S000747/1, through the Flexible Funding scheme), and of ERDF through the Interreg Atlantic Area project MONITOR (EAPA_333/2016). 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spelling 2022-07-25T12:03:06.1015038 v2 57524 2021-08-05 Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis 7032d5a521c181cea18dbb759e1ffdeb 0000-0002-6820-1680 Michael Togneri Michael Togneri true false 6fa19551092853928cde0e6d5fac48a1 0000-0001-7667-6670 Ian Masters Ian Masters true false 568e6f260489dc8139afe77757553513 Iain Fairley Iain Fairley true false 2021-08-05 MECH Acoustic Doppler current profilers (ADCPs) are the standard tool for measuring tidal currents at tidal stream energy sites; they are used to estimate several parameters, including turbulent kinetic energy (TKE). However, estimates of TKE from ADCPs are often swamped by wave action. We surmise that this bias can be detected as a data mode: to test this, we present an empirical orthogonal function (EOF) analysis of two months of TKE estimates from ADCP measurements at a tidal energy site with significant wave activity. The results of the analysis were compared with linear wave theory, using data from a wave buoy. The first data mode identified from EOF analysis agrees well with the wave bias predicted by linear theory, and the resulting decomposition of the data set into wave and turbulent components appears realistic. This decomposition is possible from ADCP data alone, and therefore offers a novel and widely applicable analysis technique for simultaneous assessment of turbulence and waves at highly-energetic tidal sites. The method can also be applied retrospectively to historical data sets. We also show that the decomposition can be improved by including higher EOF modes, but this requires an independent measurement of waves to determine the optimum number of modes. Journal Article Ocean Engineering 237 109523 Elsevier BV 0029-8018 Waves, Turbulence, Turbulent kinetic energy, Empirical orthogonal analysis, Tidal power 1 10 2021 2021-10-01 10.1016/j.oceaneng.2021.109523 COLLEGE NANME Mechanical Engineering COLLEGE CODE MECH Swansea University The authors acknowledge the support of the Welsh Assembly Government through the Sêr Cymru National Research network for Low Carbon, Energy and Environment, of EPSRC, United Kingdom through the projects SURFTEC (EP/P008628/1) and WTIMTS (funded via the Supergen ORE Hub, EP/S000747/1, through the Flexible Funding scheme), and of ERDF through the Interreg Atlantic Area project MONITOR (EAPA_333/2016). The authors also acknowledge the support of the SEACAMS and SEACAMS 2 projects, part-funded by the European Regional Development Fund through the Welsh Government 2022-07-25T12:03:06.1015038 2021-08-05T10:59:47.0010800 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering Michael Togneri 0000-0002-6820-1680 1 Ian Masters 0000-0001-7667-6670 2 Iain Fairley 3 57524__20546__d94d202743b242ecbe0276fa3cd1efe5.pdf 57524.pdf 2021-08-05T11:03:13.9816906 Output 3037423 application/pdf Version of Record true © 2021 The Authors. This is an open access article under the CC BY license true eng https://creativecommons.org/licenses/by/4.0/
title Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
spellingShingle Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
Michael Togneri
Ian Masters
Iain Fairley
title_short Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
title_full Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
title_fullStr Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
title_full_unstemmed Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
title_sort Wave-turbulence separation at a tidal energy site with empirical orthogonal function analysis
author_id_str_mv 7032d5a521c181cea18dbb759e1ffdeb
6fa19551092853928cde0e6d5fac48a1
568e6f260489dc8139afe77757553513
author_id_fullname_str_mv 7032d5a521c181cea18dbb759e1ffdeb_***_Michael Togneri
6fa19551092853928cde0e6d5fac48a1_***_Ian Masters
568e6f260489dc8139afe77757553513_***_Iain Fairley
author Michael Togneri
Ian Masters
Iain Fairley
author2 Michael Togneri
Ian Masters
Iain Fairley
format Journal article
container_title Ocean Engineering
container_volume 237
container_start_page 109523
publishDate 2021
institution Swansea University
issn 0029-8018
doi_str_mv 10.1016/j.oceaneng.2021.109523
publisher Elsevier BV
college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Mechanical Engineering
document_store_str 1
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description Acoustic Doppler current profilers (ADCPs) are the standard tool for measuring tidal currents at tidal stream energy sites; they are used to estimate several parameters, including turbulent kinetic energy (TKE). However, estimates of TKE from ADCPs are often swamped by wave action. We surmise that this bias can be detected as a data mode: to test this, we present an empirical orthogonal function (EOF) analysis of two months of TKE estimates from ADCP measurements at a tidal energy site with significant wave activity. The results of the analysis were compared with linear wave theory, using data from a wave buoy. The first data mode identified from EOF analysis agrees well with the wave bias predicted by linear theory, and the resulting decomposition of the data set into wave and turbulent components appears realistic. This decomposition is possible from ADCP data alone, and therefore offers a novel and widely applicable analysis technique for simultaneous assessment of turbulence and waves at highly-energetic tidal sites. The method can also be applied retrospectively to historical data sets. We also show that the decomposition can be improved by including higher EOF modes, but this requires an independent measurement of waves to determine the optimum number of modes.
published_date 2021-10-01T04:13:20Z
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