5.12 Computational Mesh

5.12.1 Command Status

Required.

5.12.2 Description

The computational mesh defines the horizontal spatial discretisation of the model domain and forms the geometric basis for all calculations in TUFLOW FV. Supported computational mesh model implementations are summarised in Table 5.20, with links to the relevant implementation sections below. The required commands for these implementations are summarised in Table 5.21. The following two mesh types are supported and the user is required to select one method or the other.

Table 5.20: Computational Mesh Model Implementations
Model Implementation Description
Unstructured Unstructured mesh implementation.
Structured Structured mesh implementation.
Table 5.21: Computational Mesh Commands
Command Description
Geometry 2D Conditional - Required if using an unstructured computatoinal mesh. Reads the mesh topology from a .2dm unstructured mesh file. This mesh may contain triangles, quadrilaterals, or a combination of these geometries. The mesh may also contain bathymetry and material information. Only one Geometry 2d command and mesh should be used per simulation.
Grid Origin Conditional - Required if using a structured mesh. X and Y coordinate of the grid origin.
Cell Size Conditional - Required if using a structured mesh. The model cell size which can be independent in the X and Y directions.
Grid Size Conditional - Required if using a structured mesh. The length of the X and Y grid axis.
Grid Rotation Optional - Structured grid rotation angle.

5.12.3 Unstructured Mesh

This is the usual mesh type used for TUFLOW FV modelling. TUFLOW FV supports unstructured meshes generated in the Aquaveo SMS .2dm file format. Unstructured meshes (also commonly referred to as flexible meshes) are typically used to represent complex geometries such as estuaries, rivers, and coastal systems such as the mesh shown in Figure 5.2.

Moreton Bay Unstructured Mesh (Constructed Using Aquaveo SMS)

Figure 5.2: Moreton Bay Unstructured Mesh (Constructed Using Aquaveo SMS)

Detailed instructions on how to generate unstructured meshes are provided in TUFLOW FV’s Tutorial Modules. The tutorials range in complexity, and provide general guidance on meshing with links to educational meshing resources. It is strongly recommended that these tutorials be reviewed.

Unstructured meshes are read using the Geometry 2D commands listed in Table 5.21.

! Unstructured Mesh
Geometry 2D == ..\model\geo\MB_001.2dm

5.12.4 Structured Mesh

Structured rectangular meshes, with or without rotation, are defined using the set of commands listed in Table 5.21. These meshes are useful for doing direct comparisons with other regular grid models or laboratory tests.

The Grid Rotation command defines the structured mesh rotation angle in degrees positive from East, consistent with the convention shown in Figure 5.3. The Grid Size command defines the total grid distance in the X and Y directions.

Regular Mesh Rotation Convention

Figure 5.3: Regular Mesh Rotation Convention

Structured Mesh

The below example shows the development of a 20 m resolution cartesian model. The resultant mesh is shown in Figure 5.4

! Regular grid definition
Grid Origin == 548225, 7015813 ! X origin, Y origin (m, ft or decimal degrees)
Grid Rotation == 20. ! Rotation of x axis (degrees anti-clockwise from east)
Cell Size == 100., 100. ! Cell size x, Cell size y (m, ft or decimal degrees)
Grid Size == 1000., 1000. ! Grid size x, Grid size y (m, ft or decimal degrees)

Example Regular Mesh - Cell IDs are presented at each cell centre

Figure 5.4: Example Regular Mesh - Cell IDs are presented at each cell centre