TUFLOW 2D Hydraulic Structures: Difference between revisions
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== 2D Bridges Line vs Polygon Layer ==
The form loss coefficient (FLC) is applied differently when using a line compared to a polygon.
The FLC is applied at cell sides (u and v faces) as this is where velocities are calculated. When using a polyline, the FLC attribute depends on the type of the polyline:<br>
*Thin line (width attribute of zero) - The FLC attribute in the GIS object should reflect the total form loss value for the bridge. A thin 2d_lfcsh line will apply the FLC to a single row of cell sides. As such, this approach is cell size independent. Thin line lfcsh are the easiest setup and the preferred / recommended approach.
* Thick line (width attribute between zero and 1.5 times the cell size) - The FLC attribute is half of the total loss as the form loss is applied on each cell side of the selected cells. A cell is selected if the polyline intersects the cell crosshair. Caution should be taken when using a "thick" line, due to the fact changes in cell size can trigger a "thick" line to become a "wide" line. If this were to occur the FLC attribute would need to be recalculated to not overestimate losses.
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