Tuflow

TUFLOW 2D Hydraulic Structures: Difference between revisions

Browse history interactively
← Older edit
Content deleted Content added
VisualWikitext
 
(3 intermediate revisions by one other user not shown)
Line 74:
Four flow constriction layers are represented in a 2d_lfcsh layer. The lower three layers represents the pier, the bridge deck and the rails. Each layer has its own attributes to specify the blockage and the form loss coefficient. The top (fourth) layer assumes the flow is unimpeded, representative of flow over the top of a bridge. Within the same shape, the invert of the bed, and thickness of each layer can vary in 3D.
 
The following table provides an overview for how to determine the blockage and form loss coefficient for each layer:. Note that this is just an overview and additional guidelines may need to be considered.<br>
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
Line 98:
|}
<ol>
[[File:2d_lfcsh_attributes2d_lfcsh_attributes_02.png jpg| 500px 700px]]
</ol>
<br>
Line 188:
2D BG Shape is similar to the Layered Flow Constriction, but has several updates to simplify the input based on the findings from the joint study with TMR <u>[https://tuflow.com/media/7554/2022-bridge-deck-afflux-modelling-benchmarking-of-cfd-and-swe-codes-to-real-world-data-collecutt-et-al-hwrs.pdf (Collecutt et al, 2022)]</u>.
 
The following table provides an overview of how to determine the blockage and form loss coefficient for each layer:. Note that this is just an overview and additional guidelines may need to be considered.<br>
{| style="text-align: left; margin-left: 0; " class="wikitable" width="80%"
!colspan="1" style="background-color:#005581; font-weight:bold; color:white;"| Layer
Line 381:
 
TUFLOW is a 2D solution (not 3D), in the 2d_lfcsh layer the percent blockage and form loss coefficient applied to the cell faces is depth averaged across the entire cell face (across Layer 1, 2 and 3):<br>
*For bridges, where Layer 2 has a 100% blockage applied, the minimum flow width factor of 0.001m001 (i.e. 0.1%) is used and is averaged with the Layer 1 blockage (based on the depth of the water). This may result in a water level being reported within or above the bridge deck, which would represent the pressure head.
*Layered flow constriction works by adjusting the flow area of the cell faces by any blockages to generate the correct depth averaged velocity at each face at which the form losses are applied as a fraction of the V<sup>2</sup>/2g kinetic energy. Calculating the correct velocity is critical for determining the losses as the losses are proportional to the velocity squared. <br>
*For a layered flow constriction cell face the flow area cannot be zero above the invert of Layer 1 to avoid a divide by zero in the computations, therefore after applying blockages, a minimum averagedepth averaged flow width after applying blockagesfactor of 0.001 m(i.e. 0.1%) is applied., which ifwill Layer 1 is 100% blocked,allow a very small amount of water willto flow through Layer 1. If this is unacceptable, instead of applying 100% blockage of Layer 1, the preferred approach is to start the layered flow constriction at the top of Layer 1 or raise the ground elevation to the top of Layer 1 using one of the Z Shape modification functions (e.g. a breakline). <br>
*If this is unacceptable, and a 2d_lfcsh is intended to be 100% blocked, or even just Layer 1 100% blocked in the case of a fence with a solid base, then the preferred approach is to raise the ground elevation by setting the 2d_lfcsh invert attribute higher or using a 2d_zsh Z Shape modification (e.g. a breakline). <br>
<ol>
[[File:100% Blockage Diagram.png | 500px]]
Retrieved from "https://wiki.tuflow.com/TUFLOW_2D_Hydraulic_Structures"