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Showing results for tags 'plot output'.
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Q: I want to output the flow between my 1D channel and the adjacent 2D overbank area. Will drawing a Plot Output line exactly along the 1D/2D HX boundary line provide the correct flow information? A: If you draw the Plot Output (PO) line directly on the HX line, the output may not include some of the flow that is crossing the boundary. This is because the HX line selects an entire row of cells, where one side is “active” in the 2D domain, and the other side is “inactive” in the 1D domain. The "Q_" type PO line on the other hand will select a polyline that goes along cell edges (see Figure 9-2 of the 2016-03-AE TUFLOW Manual), and there is the potential that it will select one of the sides of the HX cell where it is inactive for the 2D domain. This is demonstrated in the image below where a PO line (blue) exactly overlaps an HX boundary. The HX boundary would select entire cells (pink), where one side is inactive in the 2D domain (marked "x"). The "Q_" type PO line would select the cell sides (dashed black line). You can see that here are some locations where the PO line is selecting cell sides that aren’t active (highlighted yellow). Try digitising the PO line adacent to the HX boundary, just into the 2D domain. This should avoid selecting these inactive cell sides. Use the _TS.mif or _TS_L.shp results files to confirm which cell sides have been selected by your PO line.
Q: I've got substantial differences between my time series and plot output data and the max grids. Why is this? A: There are a few things that could be going on here, depending on the differences that you’re seeing. BIG differences (>0.1m) The max WSL level is a tracked maximum, which means that at every time step Tuflow checks the current water level at the ZC and saves it if it’s a maximum for the model run. This is then effectively a max output calculated for every time step. Compare that to the TS output which is only at your time series output interval. Similarly, a WaterRide output is an envelope of the maximum grids at every output time, not of every cell at every time step. If you’re seeing a big difference in the gridded results and the TS results, it could be that the temporal resolution in WaterRide and your TS layer maybe missing a point of instability. Investigate the mass balance at that location to see if it spikes, also try seriously reducing the time series output interval (down to something close to your timestep if possible) to see if the TS can produce the same results as the grids. Small differences There are two mechanisms used to create ascii files that can influence the difference between grid and PO. The first one is the extrapolation from the cell centers to the cell corners. Tuflow calculates the water surface level at the ZC then when you grid results using Tuflow_to_GIS. It extrapolates out to the ZH’s on the cell edges and doesn’t preserve the ZC values. This is why you get a mapped grid cell size half of your modelled grid cell size This isn’t normally an issue except where you have really steep topography or incised channels. What you can do to help this is output the ascii files within Tuflow. When you write them from within Tuflow, you get the ZC values, IE, no extrapolation. This can help reduce the difference. (You could also use HIGH RES for an output option. This means that you will get output at cell centers, mid-sides and corners, but be aware that you output size will be about 4 times the size and some programs (such as TUFLOW to GIS and dat_to_dat) don’t yet recognise this format.) The second one is the north/south orientation of the ascii grid. Ascii grids are always north/south orientated. That is, the ascii cells do not line up with your modelled orientation. Thus, there is an interpolation to rotate the grids. This can also cause issues on steep topography where there are large changes in water level or ground level. Unfortunately, there is nothing you can do to fix this one. You can look at the tuflow .dat files for raw results and confirm to yourself that the modelled results are hitting the mark and that only the presentation of results is different.