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Modelling shelf sea dynamics and estuarine circulations
YU, C.-S. (1993). Modelling shelf sea dynamics and estuarine circulations. PhD Thesis. Katholieke Universiteit Leuven. Laboratorium voor Hydraulica: Leuven. xxiii, 206 pp.

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Document type: Dissertation

Keywords
    Estuarine dynamics; Modelling; Shelf dynamics; Marine

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  • YU, C.-S.

Abstract
    Most of the studies in shelf seas and estuaries require a good description of the hydrodynamic processes in the region. This can be achieved by using a well established numerical model.
    The integration of different numerical techniques applied on high performance computers using advanced computer codes provides not only an efficient tool for coastal engineers in designing their marine constructions, but also produces more accurate and more detailed information for the environmentalists for treating the marine ecological systems. Moreover, the numerical models can help policy makers in making their decisions by providing more precise information.
    The two-dimensional (2D) depth averaged shallow water equations are used for describing the hydrodynamics in the model areas. The finite difference method has been chosen for constructing the numerical models. The physical processes involved in the hydrodynamic response are briefly described. Physical approximations for the definition of the numerical boundaries and the tidally averaged circulation, which plays a key role in understanding marine ecosystems, are introduced.
    The formulations and solution procedures of the conventional ADI schemes and two types of modified ADI schemes are described. Idealized test cases have been run by the two modified ADI schemes in order to test their numerical sensitivity. Two laboratory models were constructed for comparison with numerical results. The observed scale effect between the two physical models was identified in the numerical simulations. A high resolution numerical model for simulating the tidal flow motion in the north-west European continental shelf seas has been constructed and calibrated. Tidal motion is the dominant feature of shelf sea circulations. Tidal flow currents in the North Sea. and the English Channel are simulated by the FADI-models. Model results are presented and compared with in-situ measurements. In order to simulate more realistically the estuarine tidal flows, the treatment of moving spatial boundaries during the tidal variations is introduced to the numerical models, Idealized cases have been used to examine the moving boundary treatment. The tidal induced circulation in the Lagoon of Venice has been simulated by the FADI model. Good agreement between the model results and measurements can be observed. Another application is the numerical simulation of tidal induced currents along the Belgian coast with refined grids.
    The numerical formulation of the turbulent diffusion on an Eulerian grid is rather successful. The Eulerian description of the advection process, however, has been proven to be unsatisfactory. Since the transport processes are Lagrangian in nature, it is more accurate to describe the advection transport by Lagrangian formulations. A new trend in modelling transport processes is to combine the Lagrangian formulation for the advection, and the Eulerian approximation for the diffusion.
    Finally, the conclusions of this study are described several remarks are given, and future perspectives are outlined.

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