Numerical modelling of tidal flows around headlands and islands
This thesis presents a study of tidal flow interaction with headland and island features. Wake development in the lee of topographic features can generate complex two- and three-dimensional flow structures. The primary objectives of the research are to (i) determine the suitability of traditional numerical modelling techniques for application in the coastal environment, (ii) elucidate the development of wake features in the coastal environment, and (iii) illustrate the impact of wake features on tidal mixing and dispersion processes. A numerical finite-difference model has been developed using standard methods to solve the two-dimensional Shallow Water Equations. The model has undergone an extensive validation and verification exercise. Comparisons of model output with field data and output from other numerical simulations presented in the literature confirms the suitability of the numerical model for investigating wake and eddy development in the coastal environment. The sequence of events necessary for a wake eddy to develop from flow separation through to eddy shedding has been elucidated using idealised numerical modelling cases. Simulation and interpretation of test cases obtained from the literature has confirmed these findings. Important differences between eddy shedding events in headland and island wakes have been identified. Symmetry of the governing equations has been confirmed as the source of numerical models' failure to reproduce eddy shedding around symmetrical islands. Mixing and dispersion around a headland in a deterministic tidal flow field is simulated. Lagrangian analysis techniques are required to properly interpret transport processes. The significant impact of transient eddy features generated by the headland is indicated by the mixing and dispersion diagrams presented. A defined front between the well mixed and unmixed regions of flow is apparent. This indicates the extent of the mixing zone. Dispersion of individual patches around the headland is described using a three stage process.