Details
| Original language | English |
|---|---|
| Article number | 103751 |
| Journal | Coastal Engineering |
| Volume | 161 |
| Publication status | Published - 21 Jul 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.
ASJC Scopus subject areas
- Environmental Science(all)
- Environmental Engineering
- Engineering(all)
- Ocean Engineering
Sustainable Development Goals
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In: Coastal Engineering, Vol. 161, 103751, 21.07.2020.
Research output: Contribution to journal › Article › Research › peer review
}
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 -