Details
| Original language | English |
|---|---|
| Article number | 2636 |
| Journal | Water (Switzerland) |
| Volume | 11 |
| Issue number | 12 |
| Early online date | 13 Dec 2019 |
| Publication status | Published - Dec 2019 |
Abstract
For physical model tests, the time-varying characteristics of tidal currents are often simplified by a hydrograph following a shape of a unidirectional current or by resolving the tidal velocity signal into discrete steps of constant flow velocity. The influence of this generalization of the hydrograph's shape on the scouring process in tidal currents has not yet been investigated systematically, further increasing the uncertainty in the prediction of scour depth and rate. Therefore, hydraulic model tests were carried out to investigate and quantify the influence of the hydrograph shape on the scouring processes under tidal currents. Several different hydrographs including those with continuously changing velocities, constant unidirectional currents, square-tide velocities and stepped velocity time series were analyzed. Results show that the scouring process in tidal currents is characterized by concurrent sediment backfilling and displacement which can only be reproduced by hydrographs that incorporate a varying flow direction. However, if only a correct representation of final scour depths is of interest, similar scour depths as in tidal currents might be achieved by a constant, unidirectional current, provided that a suitable flow velocity is selected. The effective flow work approach was found capable to identify such suitable hydraulic loads with reasonable practical accuracy.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Biochemistry
- Social Sciences(all)
- Geography, Planning and Development
- Agricultural and Biological Sciences(all)
- Aquatic Science
- Environmental Science(all)
- Water Science and Technology
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In: Water (Switzerland), Vol. 11, No. 12, 2636, 12.2019.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Role and Impact of Hydrograph Shape on Tidal Current-Induced Scour in Physical-Modelling Environments
AU - Schendel, Alexander
AU - Welzel, Mario
AU - Hildebrandt, Arndt
AU - Schlurmann, Torsten
AU - Hsu, Tai-Wen
N1 - Funding Information: 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). The publication of this article was funded by the Open Access Fund of the Leibniz Universität Hannover. Furthermore, the authors thank Y. Hashemi, C. Schierl and M. Sultygov for their support in conducting the laboratory experiments and the Federal Maritime and Hydrographic Agency of Germany (BSH) for providing tidal field data from the FINO 1 platform within the RAVE (research at alpha ventus) initiative. A. Schendel was also supported by the Centre of Excellence of Ocean Engineering at the National Taiwan Ocean University in Keelung, Taiwan. Funding Information: Acknowledgments: Furthermore, the authors thank Y. Hashemi, C. Schierl and M. Sultygov for their support in conducting the laboratory experiments and the Federal Maritime and Hydrographic Agency of Germany (BSH) for providing tidal field data from the FINO 1 platform within the RAVE (research at alpha ventus) initiative. A. Schendel was also supported by the Centre of Excellence of Ocean Engineering at the National Taiwan Ocean University in Keelung, Taiwan.
PY - 2019/12
Y1 - 2019/12
N2 - For physical model tests, the time-varying characteristics of tidal currents are often simplified by a hydrograph following a shape of a unidirectional current or by resolving the tidal velocity signal into discrete steps of constant flow velocity. The influence of this generalization of the hydrograph's shape on the scouring process in tidal currents has not yet been investigated systematically, further increasing the uncertainty in the prediction of scour depth and rate. Therefore, hydraulic model tests were carried out to investigate and quantify the influence of the hydrograph shape on the scouring processes under tidal currents. Several different hydrographs including those with continuously changing velocities, constant unidirectional currents, square-tide velocities and stepped velocity time series were analyzed. Results show that the scouring process in tidal currents is characterized by concurrent sediment backfilling and displacement which can only be reproduced by hydrographs that incorporate a varying flow direction. However, if only a correct representation of final scour depths is of interest, similar scour depths as in tidal currents might be achieved by a constant, unidirectional current, provided that a suitable flow velocity is selected. The effective flow work approach was found capable to identify such suitable hydraulic loads with reasonable practical accuracy.
AB - For physical model tests, the time-varying characteristics of tidal currents are often simplified by a hydrograph following a shape of a unidirectional current or by resolving the tidal velocity signal into discrete steps of constant flow velocity. The influence of this generalization of the hydrograph's shape on the scouring process in tidal currents has not yet been investigated systematically, further increasing the uncertainty in the prediction of scour depth and rate. Therefore, hydraulic model tests were carried out to investigate and quantify the influence of the hydrograph shape on the scouring processes under tidal currents. Several different hydrographs including those with continuously changing velocities, constant unidirectional currents, square-tide velocities and stepped velocity time series were analyzed. Results show that the scouring process in tidal currents is characterized by concurrent sediment backfilling and displacement which can only be reproduced by hydrographs that incorporate a varying flow direction. However, if only a correct representation of final scour depths is of interest, similar scour depths as in tidal currents might be achieved by a constant, unidirectional current, provided that a suitable flow velocity is selected. The effective flow work approach was found capable to identify such suitable hydraulic loads with reasonable practical accuracy.
KW - Hydrograph
KW - Laboratory tests
KW - Scour
KW - Sediment transport
KW - Temporal scour development
KW - Tidal currents
KW - Unsteady flow
KW - Flow velocity
KW - Hydraulic models
KW - Ocean currents
KW - Structural geology
KW - Velocity
KW - Hydraulic model test
KW - Hydrographs
KW - Laboratory test
KW - Physical model test
KW - Practical accuracy
KW - Time-varying characteristics
KW - flow velocity
KW - hydrograph
KW - hydrological modeling
KW - laboratory method
KW - scour
KW - sediment transport
KW - tidal current
KW - unsteady flow
UR - http://www.scopus.com/inward/record.url?scp=85079675220&partnerID=8YFLogxK
U2 - 10.3390/w11122636
DO - 10.3390/w11122636
M3 - Article
VL - 11
JO - Water (Switzerland)
JF - Water (Switzerland)
SN - 2073-4441
IS - 12
M1 - 2636
ER -