Influence of tidal energy converters on sediment dynamics in tidal channel

Tidal stream turbines are one of the most advanced marine renewable energy technologies. Nonetheless, the application of the technology faces considerable challenges, as uncertainties exist about the potential impacts of these devices on the marine environment. For instance, sediment dynamics have important implications to local fauna as well as turbine foundations, design and longevity. As a result, understanding of local sediment dynamics and its impact on the environment is an important element for site assessments. However, full-scale environment surveys of tidal farms are sparse and limited, as it is at early stage of development. An alternative to study the potential impacts on the sediment transport is numerical modelling. Nevertheless, validation of these models remains challenging as it is difficult to acquire the necessary sediment data from these high-energy sites.

Hydrodynamic case studies for tidal farms exist for modeller to compare their results and insuring their models behave accurately. However, no similar case study can be found for sediment transport around tidal farms. The aim of this work is to understand the general sediment behaviour around tidal farms as well as setting a benchmark study for future modelling analysis. A series of idealised simulations, using hydrodynamic and sediment transport of MIKE21 and MIKE3 flexible mesh, are developed to investigate processes and interaction of Tidal Energy Converters (TECs) in an artificial high energetic flow system under a range of conditions (two different grain sizes, two layouts of arrays).

Findings from this study show that the 3D depth averaged velocity (DAV) is very similar to the 2D velocity: resulting in little change in bed level, less than 4% regionally, when DAV is used for sediment transport rates. However, using the bottom velocity of the 3D model generates different sediment behaviour at the vicinity of tidal arrays.