Scour around a monopile induced by directionally spread irregular waves in combination with oblique currents

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

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Externe Organisationen

  • National Taiwan Ocean University
  • Technische Universität Braunschweig
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OriginalspracheEnglisch
Aufsatznummer103751
FachzeitschriftCoastal Engineering
Jahrgang161
PublikationsstatusVeröffentlicht - 21 Juli 2020

Abstract

The progressive expansion of offshore wind energy towards greater water depths demands for an optimization of foundation structure designs to a wider range of load conditions. In offshore waters, wind driven wave irregularity and directionality become important aspects of realistic sea states. To further improve the scour prediction in marine environment a novel experimental study was conducted to investigate the influence of directionally spread (3D) irregular waves on the scouring process. The tests were carried out in the 3D wave basin of the Ludwig-Franzius-Institute, Leibniz University Hannover, Germany. A monopile structure was simulated by a transparent pile made of acrylic glass. The study was set up to progress understanding and explore dissimilarities of scour development and patterns induced by directionally spread (3D) and unidirectional (2D) waves. The model tests were complemented by tests with superimposed oblique currents. Despite identical total wave energy in terms of m0 between the directionally spread and unidirectional wave spectra, minor but distinct differences in scour depth and rate could be observed, which inevitably can only be attributed to the presence and role of the wave spread. For wave-only conditions final scour depths S/D induced by directionally spread waves were on average 33% smaller than those for unidirectional waves. Furthermore, final scour depths decreased with increasing wave spreading and displayed a growing dependency on KC numbers with increasing wave spreading. In combined wave and current conditions of up to Ucw < 0.62 scour depths were found to be slightly larger and scour progression over time faster for directionally spread than for unidirectional waves. Differences regarding the scouring rates and depths have been found to decline with flow conditions further approaching current dominated regime. A prediction approach to estimate the maximum scour depth induced by either directionally spread or unidirectional random waves is proposed. Reasonable results and insights of the present study help advancing the understanding of scour development under more realistic, i.e. natural sea-state, conditions for a more reliable design of marine and offshore infrastructure.

Schlagwörter

    Directionally spread waves, Laboratory tests, Scour, Sediment transport, Short-crested waves, Wave-current interaction, Bridge piers, Ocean currents, Offshore oil well production, Offshore power plants, Piles, Structural design, Structural optimization, Wave energy conversion, Wind power, Foundation structures, Irregular waves, Marine environment, Off-shore wind energy, Offshore infrastructure, Progressive expansion, Unidirectional waves, Wind-driven waves, design, foundation, offshore structure, pile response, reliability analysis, scour, structural analysis, wave-structure interaction, wind power, wind wave

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Scour around a monopile induced by directionally spread irregular waves in combination with oblique currents. / Schendel, Alexander; Welzel, Mario; Schlurmann, Torsten et al.
in: Coastal Engineering, Jahrgang 161, 103751, 21.07.2020.

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Schendel A, Welzel M, Schlurmann T, Hsu TW. Scour around a monopile induced by directionally spread irregular waves in combination with oblique currents. Coastal Engineering. 2020 Jul 21;161:103751. doi: 10.1016/j.coastaleng.2020.103751, 10.1016/j.coastaleng.2020.103751
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title = "Scour around a monopile induced by directionally spread irregular waves in combination with oblique currents",
abstract = "The progressive expansion of offshore wind energy towards greater water depths demands for an optimization of foundation structure designs to a wider range of load conditions. In offshore waters, wind driven wave irregularity and directionality become important aspects of realistic sea states. To further improve the scour prediction in marine environment a novel experimental study was conducted to investigate the influence of directionally spread (3D) irregular waves on the scouring process. The tests were carried out in the 3D wave basin of the Ludwig-Franzius-Institute, Leibniz University Hannover, Germany. A monopile structure was simulated by a transparent pile made of acrylic glass. The study was set up to progress understanding and explore dissimilarities of scour development and patterns induced by directionally spread (3D) and unidirectional (2D) waves. The model tests were complemented by tests with superimposed oblique currents. Despite identical total wave energy in terms of m0 between the directionally spread and unidirectional wave spectra, minor but distinct differences in scour depth and rate could be observed, which inevitably can only be attributed to the presence and role of the wave spread. For wave-only conditions final scour depths S/D induced by directionally spread waves were on average 33% smaller than those for unidirectional waves. Furthermore, final scour depths decreased with increasing wave spreading and displayed a growing dependency on KC numbers with increasing wave spreading. In combined wave and current conditions of up to Ucw < 0.62 scour depths were found to be slightly larger and scour progression over time faster for directionally spread than for unidirectional waves. Differences regarding the scouring rates and depths have been found to decline with flow conditions further approaching current dominated regime. A prediction approach to estimate the maximum scour depth induced by either directionally spread or unidirectional random waves is proposed. Reasonable results and insights of the present study help advancing the understanding of scour development under more realistic, i.e. natural sea-state, conditions for a more reliable design of marine and offshore infrastructure.",
keywords = "Directionally spread waves, Laboratory tests, Scour, Sediment transport, Short-crested waves, Wave-current interaction, Bridge piers, Ocean currents, Offshore oil well production, Offshore power plants, Piles, Structural design, Structural optimization, Wave energy conversion, Wind power, Foundation structures, Irregular waves, Marine environment, Off-shore wind energy, Offshore infrastructure, Progressive expansion, Unidirectional waves, Wind-driven waves, design, foundation, offshore structure, pile response, reliability analysis, scour, structural analysis, wave-structure interaction, wind power, wind wave",
author = "Alexander Schendel and Mario Welzel and Torsten Schlurmann and Hsu, {Tai Wen}",
note = "Export Date: 1 February 2021 Funding details: Bundesministerium f{\"u}r Wirtschaft und Technologie, BMWi, 0325575A Funding details: National Taiwan Ocean University, NTOU Funding text 1: The authors gratefully acknowledge the support of the German Federal Ministry for Economic Affairs and Energy within the funded project “Giga-Wind Life” ( BMWi : 0325575A ). Furthermore, the authors thank S. Lichte and J. Schm{\"o}kel for their support in conducting the laboratory experiments and Joshua Wessel for his help in data processing. A. Schendel was also supported by the Centre of Excellence of Ocean Engineering at the National Taiwan Ocean University in Keelung, Taiwan.",
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language = "English",
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TY - JOUR

T1 - Scour around a monopile induced by directionally spread irregular waves in combination with oblique currents

AU - Schendel, Alexander

AU - Welzel, Mario

AU - Schlurmann, Torsten

AU - Hsu, Tai Wen

N1 - Export Date: 1 February 2021 Funding details: Bundesministerium für Wirtschaft und Technologie, BMWi, 0325575A Funding details: National Taiwan Ocean University, NTOU Funding text 1: The authors gratefully acknowledge the support of the German Federal Ministry for Economic Affairs and Energy within the funded project “Giga-Wind Life” ( BMWi : 0325575A ). Furthermore, the authors thank S. Lichte and J. Schmökel for their support in conducting the laboratory experiments and Joshua Wessel for his help in data processing. A. Schendel was also supported by the Centre of Excellence of Ocean Engineering at the National Taiwan Ocean University in Keelung, Taiwan.

PY - 2020/7/21

Y1 - 2020/7/21

N2 - The progressive expansion of offshore wind energy towards greater water depths demands for an optimization of foundation structure designs to a wider range of load conditions. In offshore waters, wind driven wave irregularity and directionality become important aspects of realistic sea states. To further improve the scour prediction in marine environment a novel experimental study was conducted to investigate the influence of directionally spread (3D) irregular waves on the scouring process. The tests were carried out in the 3D wave basin of the Ludwig-Franzius-Institute, Leibniz University Hannover, Germany. A monopile structure was simulated by a transparent pile made of acrylic glass. The study was set up to progress understanding and explore dissimilarities of scour development and patterns induced by directionally spread (3D) and unidirectional (2D) waves. The model tests were complemented by tests with superimposed oblique currents. Despite identical total wave energy in terms of m0 between the directionally spread and unidirectional wave spectra, minor but distinct differences in scour depth and rate could be observed, which inevitably can only be attributed to the presence and role of the wave spread. For wave-only conditions final scour depths S/D induced by directionally spread waves were on average 33% smaller than those for unidirectional waves. Furthermore, final scour depths decreased with increasing wave spreading and displayed a growing dependency on KC numbers with increasing wave spreading. In combined wave and current conditions of up to Ucw < 0.62 scour depths were found to be slightly larger and scour progression over time faster for directionally spread than for unidirectional waves. Differences regarding the scouring rates and depths have been found to decline with flow conditions further approaching current dominated regime. A prediction approach to estimate the maximum scour depth induced by either directionally spread or unidirectional random waves is proposed. Reasonable results and insights of the present study help advancing the understanding of scour development under more realistic, i.e. natural sea-state, conditions for a more reliable design of marine and offshore infrastructure.

AB - The progressive expansion of offshore wind energy towards greater water depths demands for an optimization of foundation structure designs to a wider range of load conditions. In offshore waters, wind driven wave irregularity and directionality become important aspects of realistic sea states. To further improve the scour prediction in marine environment a novel experimental study was conducted to investigate the influence of directionally spread (3D) irregular waves on the scouring process. The tests were carried out in the 3D wave basin of the Ludwig-Franzius-Institute, Leibniz University Hannover, Germany. A monopile structure was simulated by a transparent pile made of acrylic glass. The study was set up to progress understanding and explore dissimilarities of scour development and patterns induced by directionally spread (3D) and unidirectional (2D) waves. The model tests were complemented by tests with superimposed oblique currents. Despite identical total wave energy in terms of m0 between the directionally spread and unidirectional wave spectra, minor but distinct differences in scour depth and rate could be observed, which inevitably can only be attributed to the presence and role of the wave spread. For wave-only conditions final scour depths S/D induced by directionally spread waves were on average 33% smaller than those for unidirectional waves. Furthermore, final scour depths decreased with increasing wave spreading and displayed a growing dependency on KC numbers with increasing wave spreading. In combined wave and current conditions of up to Ucw < 0.62 scour depths were found to be slightly larger and scour progression over time faster for directionally spread than for unidirectional waves. Differences regarding the scouring rates and depths have been found to decline with flow conditions further approaching current dominated regime. A prediction approach to estimate the maximum scour depth induced by either directionally spread or unidirectional random waves is proposed. Reasonable results and insights of the present study help advancing the understanding of scour development under more realistic, i.e. natural sea-state, conditions for a more reliable design of marine and offshore infrastructure.

KW - Directionally spread waves

KW - Laboratory tests

KW - Scour

KW - Sediment transport

KW - Short-crested waves

KW - Wave-current interaction

KW - Bridge piers

KW - Ocean currents

KW - Offshore oil well production

KW - Offshore power plants

KW - Piles

KW - Structural design

KW - Structural optimization

KW - Wave energy conversion

KW - Wind power

KW - Foundation structures

KW - Irregular waves

KW - Marine environment

KW - Off-shore wind energy

KW - Offshore infrastructure

KW - Progressive expansion

KW - Unidirectional waves

KW - Wind-driven waves

KW - design

KW - foundation

KW - offshore structure

KW - pile response

KW - reliability analysis

KW - scour

KW - structural analysis

KW - wave-structure interaction

KW - wind power

KW - wind wave

UR - http://www.scopus.com/inward/record.url?scp=85088629710&partnerID=8YFLogxK

U2 - 10.1016/j.coastaleng.2020.103751

DO - 10.1016/j.coastaleng.2020.103751

M3 - Article

AN - SCOPUS:85088629710

VL - 161

JO - Coastal Engineering

JF - Coastal Engineering

SN - 0378-3839

M1 - 103751

ER -

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