FLOW-3D allows users to import solids in STL
(StereoLithography) format to represent complex geometries, regardless of the
application – micro fluids, metal casting, water and environmental, aerospace,
etc. While for many industries, the STL format is a very natural and common way
of representing and sharing 3D objects, in the water and environmental
industries there is a preference towards surface-driven representations of the
environment. After all, the earth’s terrain does look like a surface for most
Raster Data Interface
In the upcoming release of FLOW-3D v11.1, we have adopted an
industry norm for terrain import: the file format known as the ESRI ASCII raster
format. The details of the format are described here.
All GIS software packages are able to export in this format. Such *.asc terrain
files will now be able to be imported directly (Figure 1) into the FLOW-3D user
Figure 1. Direct import of terrain in FLOW-3D v11.1 using ESRI ASCII raster terrain format
Subcomponent Specific Surface Roughness
Alongside terrain import, a critical modeling variable in
modeling flood wave propagation, flooding area, etc., is surface roughness. In
particular, the user needs to model local, spatially-varying surface roughness.
In FLOW-3D v11.1, users will be able to import surface roughness coefficients
in the same ASCII raster format.
More specifically, the user actually imports a raster file
of the land coverage index and provides a simple text file palette conversion
table. This table converts the type of land coverage (sand, vegetation,
built-urban, etc.) defined in the raster file to surface roughness values that are
required by the FLOW-3D solver. This gives the user a very effective way to
fine tune the surface roughness coefficients without having to regenerate the
entire raster file by simply altering the palette conversion table. The ASCII raster format was chosen because it
remains simple, yet lets the user easily control the surface coefficients that
are mapped over the domain following the land coverage types.
Figure 2. Example of overlay of terrain in FLOW-3D v11.1 Model Setup Graphical User Interface
Figure 3. Example of overlay of terrain in FLOW-3D v11.1 Model Setup Graphic User Interface
In the same framework of modeling complex flood events, functionality
to overlay actual pictures of the environment, such as river banks, built
structures, and developed housing has been added. FLOW-3D v11.1 allows users to directly texture
their terrain with corresponding imagery, typically obtained from satellite
This operation can be conducted in two stages in FLOW-3D.
The first stage is during model setup (Figures 2 and 3), so that the user can see
the context of the model he or she is building, making it easier to be sure the
simulation is properly set up. The second stage is during post-processing in
FlowSight. This is where the overlay of the flooding event and the terrain
imagery is used to reveal the extent of the flood zones and the interaction of
the flood wave with the environment.
Example Simulations and Conclusion
Figures 4 and 5 show the results from flood routing of the
streams in two different terrains. Upstream elevations have been plotted for
the example cases. Note that the analysis has been done on a terrain overlaid with
surface roughness data. The ability to import raster data and overlay it with
surface roughness provides the user a single platform, i.e., FLOW-3D, to
conduct the water and environmental studies on the terrain. Typical flood wave propagation
through a stream can be seen in Simulation 1.
Figure 4. Flood event analysis of the example in Figure 2 with overlaid surface roughness data