Influence of Different Momentum Sources on Modelling Tidal Lagoons

Tidal lagoon has gained further interest in recent years because of the increasing demand for renewable energy and their potential in providing other benefits, such as coastal protection. Accurate modelling of such schemes is essential to predict their operation, hydrodynamic and hydro-environmental processes, and power output. In this study, Telemac2D is adopted to model the tidal lagoon and then applied to the Swansea Bay lagoon which has been proposed to be built in Swansea Bay. The momentum conservation has been achieved in this model by introducing a momentum source/sink to the model. Different approaches were utilised to add momentum source that uses different source velocity in the momentum term. Another momentum term has taken the vertical gradients of the horizontal velocity into consideration. Result shows that the impact of momentum source depends on the choice of source velocity. The momentum source calculated based on the water velocity of the turbine blade resulted in the largest turbine wake, while the model without momentum term has a similar effect with the momentum velocity taken at the end of turbine diffusor. The semi-3D momentum has a slight enlarge effect in the size of turbine jet. Vortices show up on both inside and outside of the lagoon during the ebb generation. The risk of sediment deposition might happen inside the lagoon because of a large clockwise rotating vortice inside the lagoon.