Abstract Tidal sand waves are large-scale bed forms found in shallow sandy seas, which show a migration of several meters per year. Field data from the Dutch part of the North Sea revealed a migration pattern causing bidirectional migration of sand waves over a sand bank, resulting in sand wave migration uphill from both sides of the sand bank. In order to understand the physical mechanisms behind this migration behaviour, we study the inclusion of a sand bank under a sand wave field using the numerical model Delft3D. First, the schematized model set-up (i.e. schematized bathymetry and simple tidal forcing) showed that the alteration of the tidal flow by a sand bank resulted in tide-averaged horizontal flow towards the top of the sand bank, causing the bidirectional migration of sand waves over the sand bank. Second, a case study was performed in which a more complex model set-up was used (bathymetry and tidal forcing identical to a study site in the North Sea where an offshore wind farm is developed). Here, the model results revealed migration directions comparable to field observations. The results open opportunities to explore modelling migration patterns of sand wave fields for offshore wind farm development in areas with complex bathymetric environments.

中文翻译：

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沙岸潮汐沙波迁移方向数值模拟

摘要 潮汐沙波是在浅沙海中发现的大规模海床形态，每年迁移数米。来自北海荷兰部分的现场数据揭示了一种迁移模式，导致沙波在沙岸上双向迁移，导致沙波从沙岸两侧向上迁移。为了理解这种迁移行为背后的物理机制，我们使用数值模型 Delft3D 研究了沙波场下沙堤的包含。首先，模式化模型的建立（即模式化测深和简单的潮汐强迫）表明，沙堤对潮汐流的改变导致潮汐平均水平流向沙堤顶部，导致沙子的双向迁移波浪在沙岸上空。第二，进行了一个案例研究，其中使用了更复杂的模型设置（测深和潮汐力与开发海上风电场的北海研究地点相同）。在这里，模型结果揭示了与实地观察相当的迁移方向。该结果为探索用于在具有复杂测深环境的地区开发海上风电场的沙波场的建模迁移模式提供了机会。