Studying the Wake of an Island in a Macro-Tidal Estuary

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.

Predicting the dispersal of SARS-CoV-2 RNA from the wastewater treatment plant to the coast

“…The Telemac model is well-suited to vertically mixed coastal and estuarine applications due to its unstructured grid configuration that can be optimised to adequately resolve coastal topography and bathymetric features (e.g., <50 m scale) and associated near-coast dynamic circulation and mixing that are important for pollutant dispersal, and the model incorporates wetting and drying capabilities of inter-tidal regions. Telemac is used widely across the global scientific community, with recent relevant applications including Gracia et al (2018) ; Yang et al (2019) ; and Guo et al (2020) . Telemac is a hydrostatic model that computes the depth-averaged shallow water Saint-Venant equations of momentum and continuity on an unstructured triangular mesh ( Hervouet, 2007 ).…”

Hydro-epidemiological modelling of bacterial transport and decay in nearshore coastal waters

“…Note that at the time of writing, coupling between the latest release of TELEMAC-3D (v7p3r2), and the 1D river model TELEMAC-MASCARET, was not possible. Both meshes extend from the River Severn tidal limit close to Gloucester to the outer Bristol Channel close to Lundy Island, as shown in Figure 6, in order to capture the hydrodynamics of the Severn Estuary and Bristol Channel as has been widely used in previous studies (Ahmadian et al, 2014, Coz et al, 2019and Guo et al, 2020. Bathymetry data was obtained from EDINA Digimap, relative to chart datum (CD), at a 30 m grid resolution (The University of Edinburgh, 2016a, b).…”

“…The 2D mesh contained 142,533 nodes and 281,440 elements, the 3D mesh contained 133,341 nodes and 264,237 elements, repeated over 5 sigma layers giving 666,705 nodes and 1,059,648 elements in total. As for similar studies the Smagorinski turbulence closure model was used in the horizontal (Bedri et al, 2015, Abu Bakar et al, 2017b, Guo et al, 2020 and vertical directions.…”

Numerical Modelling of Oil Spill Transport in Tide-Dominated Estuaries: A Case Study of Humber Estuary, UK

“…The simulated water level showed good agreement with the recorded data (Table 4; Figure S4) resulting in an RMSE of 9.09% and 12.86% of the spring tidal range in summer and winter, respectively. Furthermore, Guo et al [106] and Maréchal [107] classify a model performance with R 2 > 0.85 as excellent…”