TUFLOW 2D Hydraulic Structures: Difference between revisions
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* <font color="blue">Read GIS Layered FC Shape</font> <font color="red">==</font> 2d_fcsh_
The TUFLOW 2D solution automatically predicts the majority of “macro” losses due to the expansion and contraction of water through a constriction, or around a bend, provided the resolution of the grid is sufficiently fine ([http://www.tuflow.com/Download/Publications/Flow%20Through%20an%20Abrupt%20Constriction%20-%202D%20Hydrodynamic%20Performance%20and%20Influence%20of%20Spatial%20Resolution,%20Barton,%202001.pdf Barton, 2001]; [http://www.tuflow.com/Download/Publications/Modelling%20of%20Bends%20and%20Hydraulic%20Structures%20in%20a%202D%20Scheme,%20Syme,%202001.pdf Syme, 2001]; [http://www.tuflow.com/Download/Technical_Memos/Modelling%20Bridge%20Piers%20in%202D%20using%20TUFLOW.pdf Ryan, 2013]). Where the 2D model is not of fine enough resolution to simulate the “micro” losses (e.g. from bridge piers, vena contracta, losses in the vertical (3rd) dimension), additional form loss coefficients and/or modifications to the cells widths and flow height need to be added. This can be done by using flow constrictions listed above.<br>
[[File:FC_Velocity_Example.PNG|400px]][[File:FC_Graph_Example.PNG|400px]]
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<ol>
<li>Calculate the ratio of the water area occupied by piers to the gross water area of the constriction (both based on the normal water surface). This value is assigned the letter J in the FHA documentation.</li>
<li>Use the FHA (1978) ''Incremental backwater coefficient for piers'' data to calculate Kp. This is the value which will be entered into TUFLOW as the form loss coefficients.<br>
[[File:FHA_Kp_arrow.PNG|400px]]
</li>
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* Line features will apply the form loss value to a single row of cells across the waterway. The TUFLOW form loss input should be entered representing the total value (eg. FC = 0.2).
* Polygon features will distribute the form loss between multiple cells across the width of the bridge and across the waterway. Due to this the TUFLOW form loss input should be entered as the total value per unit width in the direction of flow (eg. FC = 0.2/20m = 0.01).</li>
<li> flow widths (conversely, blockage factor)and flow height should updated in the <font color="blue">2d_lfcsh</font> or <font color="blue">2d_fcsh_</font> inputs. This information is used to refine the structures flow area when the model grid resolution isn't fine enough to accurately do so.
<li>The head loss across key structures should be reviewed, and if necessary, benchmarked against other methods (Recorded calibration data, HEC-RAS). Note that a well-designed 2D model will be more accurate than a 1D model, provided that any “micro” losses are incorporated.</li>
<li>TUFLOW check files should also be reviewed to confirm that the correct form losses are being applied.</li>
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