TUFLOW Remapping: Difference between revisions
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The 2020 release of TUFLOW included new Quadtree mesh and Sub-grid Sampling (SGS) functionality. The SGS feature now supports the
hydraulic analysis of partially wet cells on the flood fringe. Currently, cells that are partially wet are displayed in model output
as being fully wet.
[[File: Remap_Advice_LinkedIn.jpg ||450px|right]]
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[[File:Fig4 sgs depth interporation.png|500px]]<br>
'''Figure 4 TIN interpolation used for water depth map output with SGS.'''<br><br>
=Remapping Water Level to a Finer DEM=
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'''Figure 9 Remapped depths over a road crest from models of different mesh resolutions.'''<br><br>
As illustrated in the chart below, the DEM has a much finer resolution and the elevation changes rapidly across the road crest, so when interpolating a coarser water level grid to the finer DEM, the interpolated water level may become lower than the local DEM level. In the 2D solver, this type of location is treated as upstream controlled weir flow with the upstream depth used for the calculation. However, the information that the flow is upstream controlled is not known when remapping, hence the appearance of dry patches on the downstream face of the road crest
[[File:Fig10 road mesh size2.png|500px]]<br>
'''Figure 10 Modelled water level line over the road crest.'''<br>
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The benefits of using the combination of Quadtree mesh and Sub-grid Sampling method are many. In this page we focused on the ability of representing the sub-grid scale geometry by SGS method, which allows the user to apply a coarser mesh to reduce the total simulation time without adversely affecting the results. However, the interpolation of map output from a coarser mesh can be challenging as illustrated in the examples above. While we are developing a high resolution output feature within TUFLOW to tackle this issue, the new remapping functions of the [[ASC_to_ASC|ASC_to_ASC]] utility can be used to post process water level outputs to high resolution depth results. This produces smooth depth output along main flow paths and flood fringes. However, the SGS method and remapping tool is not a panacea, and a computational mesh with sufficient resolution is still needed to produce reasonable and meaningful simulation results, especially where high resolution velocity based map outputs are needed.<br>
'''Tip''': Run your model once with small cell size in a test mode (-t) to produce DEM_Z with all topography modifications with the same resolution as the original DEM for use in the TUFLOW Remapping function.<br>
Finally, should you have some interesting results using SGS, Quadtree or the remapping feature that you would like to share with the TUFLOW community, please feel free to email [mailto:support@tuflow.com support@tuflow.com].
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