INTRODUCTION
When the objective is to create meshes for 2D overland or marine studies, MIKE provides three distinct tools tailored to different user needs and workflows: the MIKE+ Mesh Generator, the web-based Mesh Builder application, and the MIKE Zero Mesh Generator. Each of these tools offers unique features and advantages; MIKE+ Mesh Generator is integrated within the MIKE+ modeling environment for seamless workflow, Mesh Builder enables flexible and collaborative mesh creation directly in the cloud, and MIKE Zero Mesh Generator provides a robust desktop solution with advanced editing and quality control capabilities. Together, these tools complement each other, allowing users to select the most appropriate approach for their specific project requirements, enhancing efficiency and ensuring high-quality mesh generation in complex modeling tasks.
Sections in this article:
There are two options in MIKE+, to use an existing domain file or to create the file by defining the 2D Domain directly on the map, see Figure 1. To create meshes in MIKE+ the user must have a valid license for 2D Overland modelling.
Fig. 1 – 2D Domain definition in MIKE+
MIKE+ allows the option to generate meshes on the Map View in a simple and direct fashion. In MIKE+ 2D Domain, the user must choose the option "Domain file created from MIKE+ definition". The computational grid options available in MIKE+ are the Rectangular Grid and the Flexible Mesh. The Rectangular Grid is a cartesian grid with grid cells spaced uniformly whilst the Flexible Mesh is made up of triangular or quadrangular elements of non-uniform sizes.
The fastest workflow to generate a mesh in MIKE+ is to load a polygon shape file containing the spatial distribution of the Domain extent (Layers and symbols | Add layer). Further in the 2D Domain click on the “Apply” check box to use this feature layer, and select "Apply max area". Then let the MIKE+ mesh generator builder start the triangulation by clicking on the “Generate mesh” button, see Figure 2.
Fig. 2 – 2D Domain triangulation in MIKE+
In MIKE+ it is also possible to create mesh arcs and polygon points (as in Mesh Builder and MIKE Zero Mesh Generator) and define areas with different local parameters or exclude areas from the mesh. Drawing mesh arcs and polygon markers is achieved by directly creating/editing them on the Map View using the 2D Overland tab; select the "Domain type" and in "Target layer" switch between the options for "Mesh arc" and "Mesh polygon marker" as shown in Figure 3.
Fig. 3 – Setting “Mesh arc” and “Mesh polygon marker” as Target layers in MIKE+
This mesh processing allows the user to create meshes with different triangles sizes or even exclude sections from the domain, as presented in Figure 4.
Fig. 4 – Mesh definition of varying size. Upper: definition in GUI, Lower: resulting mesh
So, when to use it?
MIKE+ allows the user to create simple meshes rapidly, however it has the delimitation that the mesh must be simple: either a rectangular grid or a triangular flexible mesh as they cannot be combined yet in MIKE+. If the user requires a combination of both type of grids, then using MIKE Mesh Builder or the MIKE Zero Mesh Generator are better options.
#2 MIKE Mesh Builder
MIKE Mesh Builder is an advanced tool to create meshes effortlessly using multiple data sources, such as aerial imagery, GIS shapefiles and elevation data. Mesh Builder contains powerful features such as extraction techniques for terrain features such as rivers, coastlines and contours and it also allows quick interpolation of elevation terrain data.
To get access to MIKE Mesh Builder the user's company must hold a “Company Subscription” to the MIKE Cloud.
MIKE Mesh Builder is often used when the user needs to create a mesh quickly and does not have much data available, e.g. by means of using the features of Open StreetMap Data (Figure 5) the user can create a functional mesh.
The readiness of open data and User Experience allows the creation meshes effectively with an adequate level of certainty.
Fig. 5 – Available feature data in Mesh Builder from Open StreetMap Data.
In contrast to MIKE+ mesh generation, in MIKE Mesh Builder the user can combine triangular elements with rectangular grids, exclude areas or define "canal-like" grids. An example is shown in Figure 6.
Fig. 6 – Example of a combined mesh created in Mesh Builder
Just as in MIKE+ mesh generation, the user can interpolate elevation data to the mesh elements with the commodity of having data from open sources already loaded to the application. As shown in Figure 7 the mesh is interpolated using GEBCO data.
Fig. 7 – Example of interpolated elevation data created in Mesh Builder
So, when to use it?
MIKE Mesh Builder is suitable for creating, editing and visualizing unstructured meshes used in hydrodynamic and environmental modelling. It has the power that can create meshes with more complexity in a rapid manner; it does not have a limitation for combining rectangular grids with unstructured meshes as MIKE+ does have. Thus, it is suitable for cases when a mesh needs to be created quickly and the user does not have enough available data, nonetheless the user can use its own data if desired.
The MIKE Mesh Builder is appropriate if the study includes complex boundaries (coastlines, rivers, roads and buildings), refining the mesh in area where rapid flow changes can be expected (i.e. structures foundations, inlets or floodplains). Furthermore, as MIKE Mesh Builder is a cloud service it allows building and managing meshes directly in the browser which enhances collaborate and remote workflows.
The Mesh Generator is a tool within the MIKE Zero platform, used to create, edit and visualize unstructured meshes. It is the most developed of the three options presented in this KA, as it was created first and contains a set of tools that enable more sophisticated workflows.
MIKE Zero Mesh Generator allows the user to create unstructured meshes both triangular and quadrilateral grids for complex domains like rivers, coastlines, floodplains and urbanized areas. Similarly to MIKE+ and MIKE Mesh Builder by means of polylines and polygons the user can define complex boundary and domain definitions. Mesh Generator has the limitation that it can only import boundary lines and polygons from .xyz files, not from shapefiles (as it can be done in MIKE+).
In MIKE Zero Mesh Generator the option of mesh refinement supports variable mesh density allowing the user to focus on points of interest as structures, bridge foundation, inlets or urban features. An example is shown in Figure 8.
Fig. 8 – Example of density varying unstructured mesh in Mesh Generator.
In MIKE Zero Mesh Generator the user must import the bathymetric/topographic data using XYZ and DEM files as scatter data to interpolate it onto the mesh nodes. This allows bathymetric integration similarly to MIKE Mesh Builder, however the user must import the elevation scatter data into MIKE Zero Mesh Generator using the Manage Scatter Data dialog presented in Figure 9.
Fig. 9 – Scatter Data Manager in MIKE Zero Mesh Generator.
To interpolate the elevation data onto the mesh the option can be found in Mesh| Interpolate. This will pop the Interpolation dialog which offers more options than the previously explained meshing tools, see Figure 10.
Fig. 10 – Interpolation options in MIKE Zero Mesh Generator
The meshes that can be generated in MIKE Zero Mesh Generator have more complexity and can be quality assured further by means of tools such as "Analyse Mesh". Here the modeler can inspect the mesh based on criteria like the smallest time step on a specific water level, smallest area or angle, leading to sound and efficient meshes. If required, the mesh can be manually edited or smoothed further.
So, when to use it?
MIKE Zero Mesh Generator is the original tool to create meshes, thus is the gold standard when one needs to create from simple to complicated meshes. It is applicable to when the user needs to create new mesh from scratch, when the modelling domain is complex and requires unstructured flexible meshing, when the user needs detailed inspection and quality refinement of the mesh and when powerful integration of GIS and bathymetric (topographic) data is demanded. In summary MIKE Zero Mesh Generator should be the option to go when the user needs full control over mesh geometry, refinement and complete integration of spatial data.
Let's say there is interest in creating a mesh for a specific area where there is not much data available. Thus, the MIKE Mesh Builder web app is suitable for this task, see Figure 11.
Fig. 11 – Drafting a mesh in MIKE Mesh Builder web app.
There is lack of information for this area, Mesh Builder offers quick and accessible information to elevation and roads geometry, and one can rapidly generate a mesh. The mesh can be downloaded by means of mention upload/download mesh via MIKE Cloud Data Admin; remember to specify the projection system for the mesh before downloading it as shown in Figure 12.
Fig. 12 – Downloading the mesh from MIKE Data Admin.
The mesh created in MIKE Mesh Builder can be opened in MIKE+ using the 2D Domain section and browsing for the mesh file. The mesh should be presented in MIKE+ Map View as shown in Figure 13.
Fig. 13 – Mesh created in Mesh Builder visualized in MIKE+.
From MIKE+ it is possible to migrate to MIKE Zero Mesh Generator. At the list of options (after clicking on the ellipsis button next to File path) just choose "Edit in Mesh generator" and the Mesh Generator window will be popped into MIKE+, as shown in Figure 14.
Fig. 14 – Opening the mesh in MIKE Zero Mesh Generator from MIKE+
The Mesh Generator popped into MIKE+ has the same tools and look and feel as the Mesh Generator while opened in MIKE Zero, as shown in Figure 15. Nonetheless the tool is more responsive while accessed from MIKE Zero.
Fig. 15 – Mesh opened in MIKE Zero Mesh Generator.
Once the mesh is opened in MIKE Zero Mesh Generator, it can be saved as a *.mdf file and this file further processed and re-opened directly from MIKE Zero. The Mesh Generator file will be saved in the same folder directory where the .mesh file is stored, as shown in Figure 16.
Fig. 16 – Mesh Generator file (.mdf file) saved together with the .mesh file.
Accessing the .mdf file opens the mesh in MIKE Zero Mesh Generator whereby means of its advanced analysis tools can be further improved, refined or modified extensively, presented in Figure 17. Note that arc editing is not possible in MIKE Zero when a predefined mesh has been exported from MIKE+, unless the original mesh was created within MIKE+ Mesh Generator (thus in MIKE Zero Mesh Generator you would be able to refine an area but not create a new mesh). To get more control of the process, one can select "Create new" using Mesh Generator and then select "Import Mesh" (from the Mesh menu in MIKE Zero Mesh Generator (when asked, choose to create arcs).
Fig. 17 – Same mesh initially created in Mesh Builder (web app) now opened in MIKE Zero Mesh Generator.
Finally, the mesh created in Mesh Generator can be imported into MIKE+ again and proceed with the 2D modelling experience.
FURTHER INFORMATION & USEFUL LINKS
[Manuals and User Guides]
MIKE Zero - Mesh Generator Step-by-step
MIKE Zero - Mesh Generator Online help
[Release Notes]
MIKEPlus Release Notes
[Scientific papers and articles]