Incipient motion of silt‐sand under combined action of waves and currents

Abstract. Coastal defence structures are often constructed to prevent beach erosion. However, poorly designed structures may cause serious erosion problems in the downdrift direction. Morphological models are useful tools to predict such impacts and assess the efficiency of defence structures for different scenarios. Nevertheless, morphological modelling is still a topic under intense research effort. The processes simulated by a morphological model depend on model complexity. For instance, undertow currents are neglected in coastal area models (2DH), which is a limitation for simulating the evolution of beach profiles for long periods. Model limitations are generally overcome by predefining invariant equilibrium profiles that are allowed to shift offshore or onshore. A more flexible approach is described in this paper, which can be generalised to 3-D models. The present work is based on the coupling of the MOHID modelling system and the SWAN wave model. The impacts of different designs of detached breakwaters and groynes were simulated in a schematic beach configuration following a 2DH approach. The results of bathymetry evolution are in agreement with the patterns found in the literature for several existing structures. The model was also tested in a 3-D test case to simulate the formation of sandbars by undertow currents. The findings of this work confirmed the applicability of the MOHID modelling system to study sediment transport and morphological changes in coastal zones under the combined action of waves and currents. The same modelling methodology was applied to a coastal zone (Costa da Caparica) located at the mouth of a mesotidal estuary (Tagus Estuary, Portugal) to evaluate the hydrodynamics and sediment transport both in calm water conditions and during events of highly energetic waves. The MOHID code is available in the GitHub repository.

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Laboratory investigations into wave period effects on sand bed erodibility under the combined action of waves and currents, by G. Voulgaris et al.: comments

Coastal Engineering ◽

10.1016/s0378-3839(96)00031-2 ◽

1997 ◽

Vol 30 (1-2) ◽

pp. 157-160 ◽

Cited By ~ 3

Author(s):

Zai-Jin You

Keyword(s):

Wave Period ◽

Period Effects ◽

Waves And Currents ◽

Combined Action ◽

Laboratory Investigations

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Sediment transport by waves and currents

Canadian Journal of Civil Engineering ◽

10.1139/l83-015 ◽

1983 ◽

Vol 10 (1) ◽

pp. 142-149 ◽

Cited By ~ 3

Author(s):

Michael C. Quick

Keyword(s):

Sediment Transport ◽

Mass Transport ◽

Power Relationship ◽

Zero Current ◽

Transport Direction ◽

Transport Velocity ◽

Waves And Currents ◽

Mass Transport Velocity ◽

Combined Action ◽

The Waves

Sediment transport is measured under the combined action of waves and currents. Measurements are made with currents in the direction of wave advance and with currents opposing the wave motion. Theoretical relationships are considered that predict the wave velocity field and the mass transport velocity for zero current and for steady currents.Following Bagnold's approach, a transport power relationship is developed to predict the sediment transport rate. Making assumptions for the mass transport velocity, the transport power is shown to agree with the measured sediment transport rates. It is particularly noted that the sediment transport direction is mainly determined by the direction of wave movement, even for adverse currents, until the waves start to break. Keywords: sediment transport, waves and currents, coastal engineering.

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Modelling of sediment transport and morphological evolution under the combined action of waves and currents

10.5194/os-2017-8 ◽

2017 ◽

Cited By ~ 1

Author(s):

Guilherme Franz ◽

Matthias T. Delpey ◽

David Brito ◽

Lígia Pinto ◽

Paulo Leitão ◽

...

Keyword(s):

Sediment Transport ◽

Morphological Changes ◽

Morphological Evolution ◽

Research Effort ◽

Beach Erosion ◽

Model Complexity ◽

Invariant Equilibrium ◽

Waves And Currents ◽

Combined Action ◽

Modelling System

Abstract. Coastal defence structures are often constructed to prevent beach erosion. However, poorly designed structures may cause serious erosion problems in the downdrift direction. Morphological models are useful tools to predict such impacts and assess the efficiency of defence structures for different scenarios. Nevertheless, morphological modelling is still a topic under intense research effort. The processes simulated by a morphological model depend on model complexity. For instance, undertow currents are neglected in coastal area models (2DH), which is a limitation for simulating the evolution of beach profiles for long periods. Model limitations are generally overcome by predefining invariant equilibrium profiles that are allowed to shift offshore or onshore. A more flexible approach is described in this paper, which can be generalised to 3D models. The present work is based on the coupling of the MOHID modelling system and SWAN wave model. The impacts of different designs of detached breakwaters and groynes were simulated in a schematic beach configuration following a 2DH approach. The results of bathymetry evolution are in agreement with the patterns found in the literature for several existing structures. The model was also tested in a 3D test case to simulate the formation of sandbars by undertow currents. The findings of this work confirmed the applicability of the MOHID modelling system to study sediment transport and morphological changes in coastal zones under the combined action of waves and currents. The same modelling methodology was applied to a coastal zone (Costa da Caparica) located at the mouth of a mesotidal estuary (Tagus Estuary, Portugal) to evaluate the hydrodynamics and sediment transport in calm water conditions and during events of highly energetic waves.

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Laboratory investigations into wave period effects on sand bed erodibility, under the combined action of waves and currents

Coastal Engineering ◽

10.1016/0378-3839(95)00026-7 ◽

1995 ◽

Vol 26 (3-4) ◽

pp. 117-134 ◽

Cited By ~ 14

Author(s):

G. Voulgaris ◽

S. Wallbridge ◽

B.N. Tomlinson ◽

M.B. Collins

Keyword(s):

Wave Period ◽

Period Effects ◽

Waves And Currents ◽

Combined Action ◽

Laboratory Investigations

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Large-Scale Experiments to Improve Monopile Scour Protection Design Adapted to Climate Change—The PROTEUS Project

Energies ◽

10.3390/en12091709 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1709 ◽

Cited By ~ 7

Author(s):

Carlos Emilio Arboleda Chavez ◽

Vasiliki Stratigaki ◽

Minghao Wu ◽

Peter Troch ◽

Alexander Schendel ◽

...

Keyword(s):

Climate Change ◽

Wind Turbine ◽

Large Scale ◽

Scale Effects ◽

Numerical Models ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Waves And Currents ◽

Combined Action ◽

Scour Protection

This study aims to improve the design of scour protection around offshore wind turbine monopiles, as well as future-proofing them against the impacts of climate change. A series of large-scale experiments have been performed in the context of the European HYDRALAB-PLUS PROTEUS (Protection of offshore wind turbine monopiles against scouring) project in the Fast Flow Facility in HR Wallingford. These experiments make use of state of the art optical and acoustic measurement techniques to assess the damage of scour protections under the combined action of waves and currents. These novel PROTEUS tests focus on the study of the grading of the scour protection material as a stabilizing parameter, which has never been done under the combined action of waves and currents at a large scale. Scale effects are reduced and, thus, design risks are minimized. Moreover, the generated data will support the development of future scour protection designs and the validation of numerical models used by researchers worldwide. The testing program objectives are: (i) to compare the performance of single-layer wide-graded material used against scouring with current design practices; (ii) to verify the stability of the scour protection designs under extreme flow conditions; (iii) to provide a benchmark dataset for scour protection stability at large scale; and (iv) to investigate the scale effects on scour protection stability.

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