Advection Dispersion Modelling: Difference between revisions
Content deleted Content added
| (9 intermediate revisions by 4 users not shown) | |||
Line 1:
=Introduction=
TUFLOW’s Advection Dispersion (AD)
TUFLOW AD is specifically oriented towards such analyses in systems including coastal waters, estuaries, rivers, floodplains and urban areas. The AD
TUFLOW FV also has Advection Dispersion functionality. In many cases, it's preferable to use TUFLOW FV for AD modelling due to its functionality with flexible mesh. See the <u>[https://docs.tuflow.com/fv/manual/latest/ TUFLOW FV Manual]</u> for details.
=Model Development=
==Setting Up a New Model==
The steps below describe the process for setting up a TUFLOW AD model. It is assumed that the user is familiar with TUFLOW Classic/HPC and that the folder structure for TUFLOW has been setup with all required files. The user should run the TUFLOW Classic/HPC model without the AD
<ol>
Line 19 ⟶ 21:
<li>Set up the boundary condition tables (.csv file(s)) to define the time-varying constituent concentrations at any input boundaries.
<ul><li>Set up the constituent boundary condition table(s) in the “bc_dbase” folder
[[File:EG17 conc 001.png]]<br></ul>
<li>Set up up the boundary condition database (.csv file)
Line 25 ⟶ 27:
[[File:EG17 AD 001.png]]<br>
<li>In the .adcf file use the "AD BC Database" command to set the location of the bc database as follows.<br><font color="blue"><tt>AD BC Database</tt></font><font color="red"><tt> == </tt></font><font color="black"><tt>..\bc dbase\my_ad_bc_dbase.csv</tt></font></ul>
<li>Setup up TUFLOW to activate the AD
<ul><li>In the .tcf file use the command "AD Control File" to set the location of the adcf and activate execution of the AD
<li>Run the model
<li>Run TUFLOW as normal. The AD
</ol>
Line 37 ⟶ 39:
= Common Questions Answered (FAQ) =
== How can the Advection Dispersion
The Advection Dispersion
To utilise the AD
== Can TUFLOW generate 2D Plot (Time-Series) Output for Advection Dispersion results? ==
Line 47 ⟶ 49:
However, results can be extracted using output zones. Defining smaller output zones allows high-frequency data to be generated for areas of interest while managing file sizes efficiently. Multiple output zones can also be used to monitor widely separated locations.
== How can initial tracer concentrations and SGS parameters be managed in the Advection Dispersion
Initial tracer concentrations can be applied to dry cells, and these concentrations are mobilised as the cells become wet during a simulation. The initial water level in dry cells is set as the bed elevation plus the Cell Wet/Dry Depth. This depth determines the initial tracer volume available for advection once the cell becomes inundated.
When SGS (Sub-Grid Sampling) is used, the initial water volume is derived from a pre-calculated “level vs cell volume” curve. Tracer concentrations are distributed across this calculated volume. This ensures accurate representation of tracer movement, even in partially wet cells.
== How can the Advection Dispersion
The Advection Dispersion
* Output Capabilities: While TUFLOW supports various output formats (e.g., XMDF, DAT, NC), extracting detailed time-series data for specific constituents at individual locations may require additional post-processing. The current AD
* Post-Processing Requirements: To obtain detailed residency time information at specific points, output zones may be required along with refined post-processing techniques. Defining output zones allows high-frequency scalar data to be captured in areas of interest, which can then be analysed to estimate residency times.
* Engine-Specific Features: Unlike the TUFLOW FV engine, which includes a particle tracking module for explicit tracking of water age, the fixed grid engine’s AD module relies on scalar-based methods to approximate residency time. For calculating water residency time with the AD
== How can the Advection Dispersion
The Advection Dispersion
For example, a model with direct rainfall over the entire domain applies a passive tracer via 2d source area (2d_sa) polygons. The output can be set up to identify areas with tracer concentrations above a certain threshold, distinguishing firewater extents from other inundated areas. Areas outside of this represent zones with zero tracer concentration. Tracers can also include decay and settling parameters for added flexibility. This method not only simplifies the process but also ensures compliance with the UK CIRIA (Construction Industry Research and Information Association) guidance by integrating rainfall and firewater scenarios into a single simulation.
== What guidance is available for Non-Newtonian mixing exponents and dispersion coefficients in the Advection Dispersion
The Non-Newtonian Mixing Exponents (m, o, and p) were introduced in the 2023-03-AC release to improve how TUFLOW models non-Newtonian fluids. These exponents control how yield stress and density change as fluid concentration varies.
Line 78 ⟶ 80:
Currently, there is no guidance for dispersion coefficients when mixing pure water with non-Newtonian fluids. Suitable values should be determined based on laboratory tests or studies specific to the fluid being modelled.
== What are the limitations of the Advection Dispersion
When using the Advection Dispersion
Flow Calculation:
Line 90 ⟶ 92:
These limitations mean that while the AD module can be used in models with 1D elements, it does not fully capture the complexities of non-Newtonian fluid behaviour in those elements. If higher accuracy is required, 2D elements where non-Newtonian properties are more comprehensively represented may be considered.
== Can the Advection Dispersion
Yes, the Advection Dispersion
TUFLOW HPC is a 2D shallow water equation solver, so it does not account for vertical salinity gradients. This means it is best suited for rivers, shallow lakes, and estuaries where haloclines are weak or absent. Different boundary inflows can be assigned varying time series of salinity concentrations, and the module will simulate how these mix over space and time.
Line 97 ⟶ 99:
If the system has strong density stratification or distinctly three dimensional flow behaviour, a fully 3D solver such as TUFLOW FV is recommended.
== Can
Yes,
Pollutants can be generated based on modelled bed shear stress, then transported through the domain using the flow field. The model can also apply decay and settling rates as part of the simulation.
The TUFLOW CATCH module, with which the Advection-Dispersion functionality is included, provides the capability to simulate pollutant runoff and transport from catchments. See the <u>[https://www.tuflow.com/products/tuflow-catch-module/ TUFLOW Website]</u> for further information.
<br>{{Tips Navigation
|uplink=[[ TUFLOW_Modelling_Guidance | Back to TUFLOW Modelling Guidance]]
}}
| |||