Three Dimensional Unstructured Finite Difference And Volume Model For Barotropic Coastal And Estuarine Circulation And Application To Hurricane Ivan 2004 And Dennis 2005

The propagation term was implemented by a semi-implicit numerical scheme, the so-called [theta]-method, for numerical stability. UFDVM exploited finite volume numerical scheme in horizontal diffusion term. Because the model used orthogonal unstructured computational grid, much flexibility to resolve complex coastal boundaries was allowed without any transformation of governing equations. The model has ability to treat wetting and drying of land. UFDVM was implemented Z-grid in vertical direction. The equilibrium turbulence model is used to determine the vertical eddy viscosity.

Three-dimensional hydrodynamic modelling of estuarine and coastal basins is an efficient means of analysing and predicting water flow characteristics for further use in sedimentation, morphological and environmental studies. To date, two-stage solution schemes have generally been used in such models, whereas in this thesis a one-stage solution formulation is introduced and applied for three-dimensional coastal hydrodynamic modelling. The governing hydrodynamic equations are reviewed in their integral form by satisfying the conservation laws of mass and momentum and rewriting them in their differential equation form for a three-dimensional spatial domain. The original continuity equation is modified for the cells in the surface layer of a multi-layer computational domain, giving rise to the establishment of the one-stage solution algorithm. The general momentum equations are rewritten, with regard to the conditions applicable to coastal waters. The integral form of the governing hydrodynamic equations have been discretized by applying the finite volume method. An orthogonal Cartesian co-ordinate system have been chosen for discretizing the computational domain. The equations have been discretized for mesh cells within the boundary and, consequently, corrections made to the discretized equations for the cells adjacent to a boundary. The one-stage solution formulation is explained in detail for solving the discretized equations using the Alternating Direction Implicit scheme. A new computer model, namely THEMFIV, has been developed for three-dimensional numerical flow simulation, based upon the one-stage algorithm. A series of experimental tests, undertaken for a laboratory model rectangular harbour, are detailed. The measured velocity values are presented to show the velocity field profile within the rectangular harbour. The numerical model has been run for several case studies to simulate (1) two-dimensional tidal circulation in the rectangular harbour, (2) three-dimensional flow.

This report investigates the use of large domains in modeling hurricane storm surge. The hydrodynamic model used in this study is the ADCJIRC-2DDI code, which is based on a two-dimensional, depth-integrated, finite element formulation. Hurricane wind stress and pressure forcing from Hurricane Kate are produced by the HURWIN code, a vertically averaged planetary boundary layer wind model. Storm surge predictions are conducted over three computational domains, which have varying sizes. The smallest domain covers the continental shelf, another domain includes the Gulf of Mexico, and the final domain is quite large and extends into the deep ocean. Domains over the continental shelf and the Gulf of Mexico are shown to be inadequate for modeling hurricane storm surge. On the contrary, a large domain, which includes the Western North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico, is optimal for use with storm surge models. The influence of an inverted barometer condition applied at the open boundary is examined for each computational domain. Circulation model, Numerical model, Finite element method, Storm surge model, Hurricane surge model, Two-dimensional model, Hydrodynamic model.

This article is the second of a two-part paper on ELCIRC, an Eulerian-Lagrangian finite difference/finite volume model designed to simulate 3D baroclinic circulation across river-to-ocean scales. In part one (Zhang et al., 2004), we described the formulation of ELCIRC and assessed its baseline numerical skill. Here, we describe the application of ELCIRC within CORIE, a coastal margin observatory for the Columbia River estuary and plume. We first introduce the CORIE modeling system and its multiple modes of simulation, external forcings, observational controls, and automated products. We then focus on the evaluation of highly resolved, year-long ELCIRC simulations, using two variables (water level and salinity) to illustrate simulation quality and sensitivity to modeling choices. We show that, process-wise, simulations capture well important aspects of the response of estuarine and plume circulation to ocean, river, and atmospheric forcings. Quantitatively, water levels are robustly represented, while salinity intrusion and plume dynamics remain challenging. Our analysis highlights the benefits of conducting model evaluations over large time windows (months to years), to avoid significant localized biases. The robustness and computational efficiency of ELCIRC has proved invaluable in identifying and reducing non-algorithmic sources of errors, including parameterization (e.g., turbulence closure and stresses at the air- water interface) and external forcings (e.g., ocean conditions and atmospheric forcings).

This report describes the application of model ADCIRC-2DDI, a two- dimensional, depth-integrated, finite-element-based hydrodynamic circulation code, to the western North Atlantic, Gulf of Mexico and Caribbean Sea in order to develop a tidal constituent database. Issues that are emphasized in the development of the Western North Atlantic Tidal (WNAT) model include the definition of hydrodynamically simple open ocean boundaries; the use of large domains; the importance of a high degree of grid resolution in coastal regions; and the use of finite element meshes with highly varying nodal densities in order to minimize the size of the discrete problem. The development of an optimal graded finite element mesh is based on regular and graded grid convergence studies using an M2 tidal forcing function on the boundary and within the domain. The optimal graded mesh is then forced for eight diurnal and semidiurnal astronomical tidal constituents (K1, O1, PI, Ql, M2, S2, N2, and K2) on the open ocean boundary by coupling to Schwiderski's (1979; 1981 a-g) global model results as well as within the interior domain using a tidal potential forcing function. The structure of the various tides is examined and results are compared to field data at 77 stations ... Bottom stress, Finite element method, Three-dimensional model, Circulation model, Hydrodynamic model, Two-dimensional model, Direct stress solution, Numerical model.