University of Twente Student Theses


Modelling the hydrodynamic effects of the construction of a small island near the Wadden sea.

Zhou, Y. (2023) Modelling the hydrodynamic effects of the construction of a small island near the Wadden sea.

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Abstract:This study investigates the hydrodynamical effects of a small energy island in the eastern Dutch coastal waters. This energy island is part of an ongoing investigation to accommodate wet infrastructure (cables, pipelines, etc) that connects offshore windfarms to the main land. The study area is located near the mouth of the Ems estuary, west of the German barrier island ‘Borkum’ and north of the Dutch Wadden barrier island ‘Rottumeroog’. The seabed of the study area is locally very dynamic, with areas where the seabed has seen variations of as much as 10 m in about 40 years. The seabed mobility is of importance to the selection of the optimal location of the foreseen energy island. Even though parts of the shoal on which the island is planned to be built (the Ballonplaat) has been relatively stable the past few decades, it is yet not unknown whether this will be the case in the future. Additionally, the hydrodynamics in the area can be quite severe, especially during winter storms with high waves. These overall characteristics of the study area are described in chapter 2 along with some theory concerning waves as waves are the major forcing that is active in the area, along with the tidal currents. To minimize the impacts of the energy island, adjustments can be made to the design and features. Some examples of these features are the shape and orientation of the island. Island designs and features are presented and discussed in chapter 3, where it is also explained how a specific island design can be implemented to a Delft3D model. By modelling various island designs, the effects on the flow and waves in the area is studied. The output of computations with an existing Delft3D model of the Wadden Sea and Ems estuary is used for the analysis. The main parameters and assumptions underlying the Delft3D model are discussed in chapter 4. In this chapter, the computed currents for the situation without an island are also presented. Furthermore , a comparison is made between the waves that are computed with a 2D SWAN model along a given transect and computations that were done in this study with several theoretical 1D wave models for the same seabed profile along the transect as well as for simpler linear bed profiles. The simulations with the Delft3D-SWAN model showed the effects of an island on the depth�averaged current velocity patterns and significant wave height, which are discussed in chapter 5. The results show that, while the addition of an island presents clear changes in the flow patterns, the impact on the significant wave height is relatively small. The individual effects of the island parameters, including size and orientation, are also investigated, but revealed to be difficult to consider independently.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
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