High-resolution, unstructured meshes for hydrodynamic models of the Great Barrier Reef, Australia (original) (raw)
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This study investigates the design of unstructured mesh resolution and its impact on the modeling of barotropic tides along the United States East Coast and Gulf Coast (ECGC). A discrete representation of a computational ocean domain (mesh design) is necessary due to finite computational resources and an incomplete knowledge of the physical system (e.g., shoreline and seabed topography). The selection of mesh resolution impacts both the numerical truncation error and the approximation of the system's physical domain. To increase confidence in the design of highresolution coastal ocean meshes and to quantify the efficacy of current mesh design practices, an automated mesh generation approach is applied to objectively control resolution placement based on a priori information such as shoreline geometry and seabed topographic features. The simulated harmonic tidal elevations for each mesh design are compared to that of a reference solution, computed on a 10.8 million vertex mesh of...
A high-resolution model of the Hydrodynamics of the whole Great Barrier Reef
2007
An unstructured-mesh parallel hydrodynamical model of the whole Great Barrier Reef is presented. The depth-averaged equations of motion are discretized in space by means of a mixed finite element formulation while the time marching procedure is based on a third order explicit Adams-Bashforth scheme. The mesh is made up of triangles. The size and the shape of the triangles can be modified easily so as to resolve a wide range of scales of motion, from those of the regional flows to those of the eddies or tidal jets that develop in the vicinity of reefs and islands. The forcings are the surface wind stress, the tides and the East Australian Current, the latter two forcings being applied along the open boundaries of the computational domain. The numerical results compare favourably with observations of both alongshores currents due to the East Australian Current and the local pertubations due to narrow reef passages. Comparisons are also performed with the simulations of a three-dimensi...
Two‐dimensional, unstructured mesh generation for tidal models
International Journal for Numerical Methods in Fluids, 2001
The successful implementation of a finite element model for computing shallow-water flow requires the identification and spatial discretization of a surface water region. Since no robust criterion or node spacing routine exists, which incorporates physical characteristics and subsequent responses into the mesh generation process, modelers are left to rely on crude gridding criteria as well as their knowledge of particular domains and their intuition. Two separate methods to generate a finite element mesh are compared for the Gulf of Mexico. A wavelength-based criterion and an alternative approach, which employs a localized truncation error analysis (LTEA), are presented. Both meshes have roughly the same number of nodes, although the distribution of these nodes is very different. Two-dimensional depth-averaged simulations of flow using a linearized form of the generalized wave continuity equation and momentum equations are performed with the LTEA-based mesh and the wavelength-to-gridsize ratio mesh. All simulations are forced with a single tidal constituent, M 2. Use of the LTEA-based procedure is shown to produce a superior (i.e., less error) two-dimensional grid because the physics of shallow-water flow, as represented by discrete equations, are incorporated into the mesh generation process. Copyright
A multi-scale model of the hydrodynamics of the whole Great Barrier Reef
2008
An unstructured-mesh parallel hydrodynamic model of the whole Great Barrier Reef is presented. This model simultaneously simulates most scales of motion. It allows interactions between small-and large-scale processes. The depth-averaged equations of motion are discretized in space by means of a mixed finite element formulation while the time-marching procedure is based on a third order explicit Adams–Bashforth scheme. The mesh is made up of triangles.
Geoscientific Model Development Discussions, 2018
OceanMesh2D is a set of user-friendly MATLAB functions with pre-and post-processing utilities to generate twodimensional (2D) unstructured meshes for coastal ocean circulation models. These meshes are generated according to a variety of feature driven geometric and topo-bathymetric mesh size functions, which are controlled by user-defined parameters. Mesh generation is achieved through a force-balance algorithm to locate vertices and a number of topological improvement strategies aimed at improving the worst case triangle quality and adjusting the shoreline representation. The software embeds the mesh generation process into an object-orientated framework that facilitates rapid workflows on personal computers. These workflows are flexible, reproducible, and script-able. Through real world examples, we illustrate the various capabilities of the software and demonstrate how it can produce high-quality, multiscale, unstructured meshes that are faithful to a variety of constraints and automatically conform to arbitrary shoreline vector datasets. The objective of this paper is to describe the functionality of the software.
A systematic approach to unstructured mesh generation for ocean modelling using GMT and Terreno
Computers & Geosciences, 2008
A systematic approach to unstructured mesh generation for ocean modelling is presented. The method optimises unstructured meshes to approximate bathymetry to a user specified accuracy which may be defined as a function of longitude, latitude and bathymetry. GMT (Generic Mapping Tools) is used to perform the initial griding of the bathymetric data. Subsequently, the Terreno meshing package combines automated shoreline approximation, mesh gradation and optimisation methods to generate highquality bathymetric meshes. The operation of Terreno is based upon clearly defined error measures and this facilitates the automation of unstructured mesh generation while minimising user intervention and the subjectivity that this can introduce.
A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes
International Journal for Numerical Methods in Fluids, 2008
A new modelling framework is presented for application to a range of three-dimensional (3D) multi-scale oceanographic problems. The approach is based upon a finite element discretization on an unstructured tetrahedral mesh which is optimized to represent highly complex geometries. Throughout a simulation the mesh is dynamically adapted in 3D to optimize the representation of evolving solution structures. The adaptive algorithm makes use of anisotropic measures of solution complexity and a load-balanced parallel mesh optimization algorithm to vary resolution and allow long, thin elements to align with features such as boundary layers. The modelling framework presented is quite different from the majority of ocean models in use today, which are typically based on static-structured grids. Finite element (and volume) methods on unstructured meshes are, however, gaining popularity in the oceanographic community. The model presented here is novel in its use of unstructured meshes and anisotropic adaptivity in 3D, its ability to represent a range of coupled multi-scale solution structures and to simulate non-hydrostatic dynamics.
Automatic improvement of unstructured grids for coastal simulations
The generation of unstructured triangular grids for coastal applications requires extensive manual tunning, in order to improve the stability, accuracy and efficiency of the model simulations. As current grids reach 10 5-10 6 nodes, this manual tunning is no longer feasible. This paper presents a new post-processor that aims at optimizing the local distribution of nodes and elements by adding and deleting nodes and by changing the connections between nodes. The algorithms target a smooth transition between elements sizes by making the number of connections of each internal node as close to 6 as possible. An application of the post-processor to various grids shows that the grid roughness is reduced by 10-30%, while decreasing marginally the number of nodes and maintaining the global nodal distribution. To illustrate the benefits of the post-processor, a grid with 130.000 nodes of the maritime zone under Portuguese jurisdiction is used to simulate tides with a good accuracy (root mean square errors below 10 cm) and without numerical oscillations. The model results provide an extensive database of tidal elevations that can feed boundary conditions to local estuarine models.