Variability of sediment processes around a tidal farm in a theoretical channel

Abstract

Sediment transport plays a crucial role in coastal ecosystems and is one of the least known parameters in high energy sites. The recent development of tidal energy projects challenges the scientific community to better understand this natural phenomenon and the interactions with tidal turbines. Using MIKE21/3 software from DHI, a benchmark for sediment transport model was developed with simulations with and without a tidal farm in idealised two and three-dimensional tidal channels. Results reveal that a 2D approach is sufficient for regional scale morphological assessments, however 3D models allow for a closer examination of influences around the tidal farm. Differences in calculating sediment transport rates based on approaches after Engelund & Fredsøe and Van Rijn formulae illustrate the degree of uncertainty in modelling sediment transport rates. Results for the Engelund & Fredsøe models also show that they are sensitive to mesh resolution in equilibrium conditions and are more stable in non-equilibrium conditions for the bed level change rates. Tests have also demonstrated that models using Engelund & Fredsøe formulae are more sensitive to physical characteristics than models based on Van Rijn, accentuating the necessity to evaluate sediment transport formulae with field data before making a choice of model.

Modeling Morphodynamic Impacts and Optimization of Marine Hydrokinetic Arrays in Shallow Offshore Environments

“…Auguste et al [29] conducted a comprehensive study involving the development of 2D and 3D sediment transport models, examining the presence and absence of tidal turbines to gain a deeper understanding of sediment interactions within tidal farms. These models were implemented using the MIKE21/3 software from DHI, and sediment transport rates were computed utilizing the formulations by Engelund and Fredsøe (EF) and Van Rijn (VR), under both equilibrium and non-equilibrium conditions.…”

UK perspective research landscape for offshore renewable energy and its role in delivering Net Zero

“…In shallow estuaries, the change in flow from tidal energy facilities can create sediment morphological change. These sediment transport phenomena can affect the function of ORE systems and can also impact on habitat and ecosystems (Auguste et al 2021). However, if the changes to water flow, sediment and habitat can be predicted, confidence in design and social acceptability will be raised.…”

Modelling Morphological Changes and Migration of Large Sand Waves in a Very Energetic Tidal Environment: Banks Strait, Australia

“…For the pure current cases, three different sediment transport formulae were tested: Van Rijn (VR) equations [60,80] in equilibrium and non-equilibrium mode and Engelund and Fredsøe (EF) [65] in non-equilibrium mode. The EF formula in equilibrium mode was not tested, given the instability [81] found in their sensitivity tests for energetic sites. For the three cases with current forcing only, the migration of crests and troughs was not well represented as shown in Figure 13.…”

“…The sand waves were totally flattened, and the bottom of the seabed was lower with the EF formula. Auguste [81] found that the EF formula was more sensitive to basic physical properties, such as strong currents, than the VR formula and may not be suitable in a highly energetic site. For the reference scenario (wave + current) the depth-averaged current was reduced up to 0.1 m/s with an average reduction of 0.02 m/s for the profile AA'.…”