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.
[[File:FC_Velocity_Example.PNG|400px]][[File:FC_Graph_Example.PNG|400px]]
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Form loss coefficients are an important input to the flow constriction layers. TUFLOW form loss coefficients can be derived from information in publications such as ''Hydraulics of Bridge Waterways'' ([http://www.ciccp.es/ImgWeb/Castilla%20y%20Leon/Documentaci%C3%B3n%20T%C3%A9cnica/Hydraulics%20of%20Bridge%20Waterways%20(1978).pdf FHA, 1973]). For example, backwater caused by introduction of piers in a bridge constriction is dependent on the ratio that the area of the piers relative to the gross area of the bridge opening, the type of piers (or piling in the case of pile bents) and the angularity of the piers with the direction of flood flow.
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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.
[[File:FHA_Kp.PNG|400px]]
</li>
<li>Digitise <font color="blue">2d_lfcsh</font> or <font color="blue">2d_fcsh_</font> inputs using either a line or polygon feature. When applying form loss coefficients the best approach is to view the structure as a collection of 2D cells representing the whole structure, rather than being too specific about the representation of each individual cell:
* 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).
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