Abstract
Tidal flow can generate unsteady wakes, large eddies, and recirculation zones in the lee or around complex natural and artificial obstructions, such as islands, headlands, or harbours. It is essential to understand the flow patterns around such structures given the potential impacts they can have on sedimentation, the marine environment, ecology, and anthropogenic activities. In this paper, the wake around an island in a macro-tidal environment has been studied using a widely used hydro-environmental model, Telemac-2D. Current data collected using moored acoustic Doppler current profilers (ADCPs) were used to validate and refine the Telemac-2D model. Four different turbulence models and several different solver options for the k- ε model were tested in this study to assess which representation could best replicate the hydrodynamics. The classic k- ε model with the solver of conjugate residual was the most suitable method to simulate the wake in the lee of the island. The model results showed good correlation with measured data. The island wake parameter used to predict the wake behaviour and its predictions matched the model results for different tidal conditions, suggesting that the island wake parameter could be used to predict the wake behind obstacles in macro-tidal environments. The model predictions showed the development of a wake is similar between ebb and flood tides in the neap tide while showing more difference in spring tide. With the increase of velocity in the neap tide, two side-by-side vortices will appear and then changing to stable Karman Vortex Street. During the ebb phase of spring tide, the wake will develop from a stable vortex to an unstable Karman Vortex Street, while the wake remained stable with two vortices during an flood tide.
Highlights
Understanding tidal flow around natural or artificial obstacles, such as islands, headlands, harbours, and coastal reservoirs, is an important challenge in coastal, estuarine, and river basins due to the potential impacts of such flows on the environment and ecology in the basin [1]
The model performance was validated using water levels at four tidal gauge sites across the modelling domain. Water levels at these sites were acquired from British Oceanographic Data Centre (BODC) tidal gauges (Figure 1)
For the acoustic Doppler current profilers (ADCPs) data collected on 5 July 2011 at 10:49, the model behaves well in the low-velocity zone, which corresponds to the recirculation zone in the lee of the island
Summary
Understanding tidal flow around natural or artificial obstacles, such as islands, headlands, harbours, and coastal reservoirs, is an important challenge in coastal, estuarine, and river basins due to the potential impacts of such flows on the environment and ecology in the basin [1]. It is important to validate accurate representation of the hydrodynamic and the barrage or lagoon location are of crucial numerical model performance relating to island wake behaviour in a macro-tidal estuary. To assess the importance model in terms the impact the hydro-environment in the region [26,27,28] It is best turbulence forofisland wakeon predictions, the Telemac-2D model predictions were obtained important to validate the numerical model performance relating to island wake and compared for four turbulence models and six solvers, with all of the predictions being compared behaviour in a macro-tidal estuary. Wakes the calibrated model could be applied modelling other coastal structures suchThe as offshore lagoons generated in setting the lee of the island underin various tidal conditions were studied. Applicable to comparable schemes; for example, the calibrated model setting could be applied in modelling other coastal structures such as offshore lagoons and coastal reservoirs
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