Tutorial Module06 Archive: Difference between revisions

==Revise the Road Crest==

Currently a 2d_zsh layer (created in Module 3) is used to raise the zpts along the line and length of the northern road up to the road deck levels. This part of the tutorial will use 2d_zsh layers to regrade the road embankment. The road crest elevation will be amended and parts of the embankment lowered at the location of the 2D bridge. Follow the instructions at the relevant link below for your GIS package.

 

==Bridge Modelling Option 1: 1D Bridge with 2D Weir Overflow==

For the first of our three bridge modelling techniques we will represent the flow area under the bridge up to the bridge soffit, the piers and energy losses through the structure using a 1D bridge channel. Bridge surcharge will be modelled in the 2D domain in a similar manner to the current 1D/2D culvert modelling approach. We have provided the required bridge cross section and bridge loss coefficient with height table (xs_bridge.csv and lc_bridge.csv respectively). Importantly, the highest elevation in the bridge cross-section is set at the soffit level of the bridge opening. The loss coefficient table defines the fraction of the kinetic energy (V²/2g) that is lost due to obstructions such as piers and the bridge deck. These loss coefficients have been developed with reference to the methods outlined Hydraulics of Bridge Waterways (Bradley, 1978). Open the csv files to understand how the bridge is modelled within TUFLOW (you may wish to produce a scatter plot of the cross section file to help visualise the bed profile). To update the model follow the instructions at the relevant link below for your GIS package.

 

==Bridge Modelling Option 2: 1D Bridge with 1D Weir Overflow==

Using this approach we will use the 1D bridge section developed for Option 1 to represent the flow area under the bridge (as such please ensure you have completed Bridge Option 1). For this option, instead of using the 2D DEM to model bridge surcharge, we will create a 1D weir channel. This method requires us to modify a number of files including our 2D domain and 1D/2D boundary layers in the region between the cross sections immediately upstream and downstream of the structure.

Follow the instructions at the relevant link below for your GIS package.

 

==Bridge Modelling Option 3: 2D Layered Flow Constriction==

Finally, we can also model the obstruction and losses caused by the bridge in 2D only, using a layered flow constriction. We have provided the location of the layered flow constriction to be used to model the replacement bridge on the northern road. This data is in the Module Data folder under '''Module_Data\Module_06\2D_Bridge'''. Three GIS layers are provided: one with a polygon defining the 2D cells over which the flow constriction is to be applied, another containing height and depth points for the layers below and immediately above the bridge obvert and the third to lower the 2D grid cells at the bridge location. Follow the instructions at the relevant link below for your GIS package.

 

For application of 2D layered flow constriction form losses, a handy reference is the Technical Memo on modelling bridge piers in 2D using TUFLOW available at: http://www.tuflow.com/Library.aspx?TechnicalDocuments

=Modify Simulation Control Files and Set-up a TUFLOW Scenario=

Now that we have made all of the necessary changes to the GIS layers, we need to update our control files to include the option of modelling the replacement bridge.

 

=Run the Simulation=

This section contains links to some possible problems that may occur when progressing through Module 6. If you experience a problem that is not detailed, please email support@tuflow.com or add and describe the problem on the <u>[[Talk%3ATutorial_Module06_Archive | discussion page.]]</u><br>

 

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