TUFLOW 1D Channels and Hydraulic Structures: Difference between revisions
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The velocity and bed shear stress reported in the 2D domain at a pipe outlet depends on the model cell size. If the cell size is small enough and any outlets structures (i.e. wingwalls) are properly represented by the 2d cell/face elevations, TUFLOW can reasonably represent the flow field at the pipe outlet and estimate the bed shear stress base on the manning’s equation. However, be aware that TUFLOW solves 2D depth-averaged shallow water equation, so there is limitation of using it to estimate bed shear stress around complex structures or geometry that could experience vertical acceleration or re-circulation.
== How do I model blockage for irregular shaped culverts or channels? ==
For irregular shaped culverts and channels using the I type cross section in the 1d_xs layer, a alternative method to simulate blockage is by applying a Skew attribute. This reduces the effective flow width of the cross section by rotating it relative to the direction of flow and can be used to approximate reduced capacity due to debris or structural blockage.
A skew angle of 0 means the cross section is aligned with the flow. As the angle increases, the effective width is reduced. For example, a skew of 45 degrees results in a square root of 2 reduction in width (cos 45 degrees). While this does reduce conveyance, the relationship is not one to one with percentage blockage, as conveyance also depends on flow area, hydraulic radius, and Mannings n.
For more control over blockage representation, the pBlockage attribute is recommended where available (for example with circular culverts or 2D HX lines). However, for irregular shapes where pBlockage is not supported, using Skew provides an alternative.
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